Added CONTRIBUTING.md (#2663)

* [WIP] Added CONTRIBUTING.md

* Updated CONTRIBUTING.md

* Update

CONTRIBUTING.md

+# Contributing to Torchvision
+
+We want to make contributing to this project as easy and transparent as possible.
+
+## TL;DR
+
+We appreciate all contributions. If you are interested in contributing to Torchvision, there are many ways to help out. 
+Your contributions may fall into the following categories:
+
+- It helps the project if you could 
+    - Report issues you're facing
+    - Give a :+1: on issues that others reported and that are relevant to you 
+
+- Answering queries on the issue tracker, investigating bugs are very valuable contributions to the project.
+
+- You would like to improve the documentation. This is no less important than improving the library itself! 
+If you find a typo in the documentation, do not hesitate to submit a GitHub pull request.
+
+- If you would like to fix a bug
+    - please pick one from the [list of open issues labelled as "help wanted"](https://github.com/pytorch/vision/issues?q=is%3Aopen+is%3Aissue+label%3A%22help+wanted%22)
+    - comment on the issue that you want to work on this issue
+    - send a PR with your fix, see below. 
+
+- If you plan to contribute new features, utility functions or extensions, please first open an issue and discuss the feature with us.
+
+## Issues
+
+We use GitHub issues to track public bugs. Please ensure your description is
+clear and has sufficient instructions to be able to reproduce the issue.
+
+## Development installation
+
+### Install PyTorch Nightly 
+
+```bash
+conda install pytorch -c pytorch-nightly
+# or with pip (see https://pytorch.org/get-started/locally/)
+# pip install numpy
+# pip install --pre torch -f https://download.pytorch.org/whl/nightly/cu102/torch_nightly.html
+```
+
+### Install Torchvision
+
+```bash
+git clone https://github.com/pytorch/vision.git
+cd vision
+python setup.py install
+# or, for OSX
+# MACOSX_DEPLOYMENT_TARGET=10.9 CC=clang CXX=clang++ python setup.py install
+# for C++ debugging, please use DEBUG=1
+# DEBUG=1 python setup.py install
+pip install flake8 typing mypy pytest scipy
+```
+You may also have to install `libpng-dev` and `libjpeg-turbo8-dev` libraries:
+```bash
+conda install libpng jpeg
+```
+
+## Development Process
+
+If you plan to modify the code or documentation, please follow the steps below:
+
+1. Fork the repository and create your branch from `master`.
+2. If you have modified the code (new feature or bug-fix), please add unit tests.
+3. If you have changed APIs, update the documentation. Make sure the documentation builds.
+4. Ensure the test suite passes.
+5. Make sure your code passes `flake8` formatting check.
+
+For more details about pull requests, 
+please read [GitHub's guides](https://docs.github.com/en/github/collaborating-with-issues-and-pull-requests/creating-a-pull-request). 
+
+If you would like to contribute a new model, please see [here](#New-model).
+
+If you would like to contribute a new dataset, please see [here](#New-dataset). 
+
+### Code formatting and typing
+
+New code should be compatible with Python 3.X versions and be compliant with PEP8. To check the codebase, please run
+```bash
+flake8 --config=setup.cfg .
+```
+
+The codebase has type annotations, please make sure to add type hints if required. We use `mypy` tool for type checking:
+```bash
+mypy --config-file mypy.ini
+```
+
+### Unit tests
+
+If you have modified the code by adding a new feature or a bug-fix, please add unit tests for that. To run a specific 
+test: 
+```bash
+pytest test/<test-module.py> -vvv -k <test_myfunc>
+# e.g. pytest test/test_transforms.py -vvv -k test_crop
+```
+
+If you would like to run all tests:
+```bash
+pytest test -vvv
+``` 
+
+### Documentation
+
+Torchvision uses [Google style](http://sphinxcontrib-napoleon.readthedocs.io/en/latest/example_google.html)
+for formatting docstrings. Length of line inside docstrings block must be limited to 120 characters.
+
+Please, follow the instructions to build and deploy the documentation locally.
+
+#### Install requirements
+
+```bash
+cd docs
+pip install -r requirements.txt
+```
+
+#### Build
+
+```bash
+cd docs
+make html
+```
+
+#### Local deployment
+
+Please, use python 3.X for the command below:
+```bash
+cd docs/build/html
+python -m http.server <port>
+# e.g. python -m http.server 1234
+```
+Then open the browser at `0.0.0.0:<port>` (e.g. `0.0.0.0:1234`)
+
+### New model
+
+More details on how to add a new model will be provided later. Please, do not send any PR with a new model without discussing 
+it in an issue as, most likely, it will not be accepted.
+ 
+### New dataset
+
+More details on how to add a new dataset will be provided later. Please, do not send any PR with a new dataset without discussing 
+it in an issue as, most likely, it will not be accepted.
+
+### Pull Request
+
+If all previous checks (flake8, mypy, unit tests) are passing, please send a PR. Submitted PR will pass other tests on 
+different operation systems, python versions and hardwares.
+
+For more details about pull requests workflow, 
+please read [GitHub's guides](https://docs.github.com/en/github/collaborating-with-issues-and-pull-requests/creating-a-pull-request).
+
+## License
+
+By contributing to Torchvision, you agree that your contributions will be licensed
+under the LICENSE file in the root directory of this source tree.

README.rst

@@ -136,7 +136,8 @@ You can find the API documentation on the pytorch website: https://pytorch.org/d
 
 Contributing
 ============
-We appreciate all contributions. If you are planning to contribute back bug-fixes, please do so without any further discussion. If you plan to contribute new features, utility functions or extensions, please first open an issue and discuss the feature with us.
+
+See the [CONTRIBUTING](CONTRIBUTING.md) file for how to help out.
 
 Disclaimer on Datasets
 ======================