[Nova] New GHA Workflow for Docstring Sync (#2720)

Summary:
Create a standalone GitHub Actions workflow for Docstring Sync. This job (https://app.circleci.com/pipelines/github/pytorch/audio/12625/workflows/96223ad2-0fcd-4dae-a045-d530aaf9b55c/jobs/907466) currently depends on linux wheels builds, which creates a dependency that makes the migration to Nova trickier. This PR creates a fresh standalone workflow for this job that is triggered per-PR and before nightly/release cuts.

Pull Request resolved: https://github.com/pytorch/audio/pull/2720

Reviewed By: izaitsevfb, seemethere

Differential Revision: D39863574

Pulled By: osalpekar

fbshipit-source-id: 8599dc006693242278857a3dedeb4fddc1eed14b

.github/workflows/docstring_parameters_sync.yml

+name: Docstring Parameters Sync
+on:
+  pull_request:
+  push:
+    branches:
+      - nightly
+  workflow_dispatch:
+jobs:
+  check-docstring-sync:
+    name: "Check whether the docstring parameters are in-sync"
+    runs-on: ubuntu-latest
+    container:
+      image: pytorch/conda-builder:cpu
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v2
+      - name: Setup Minconda
+        uses: conda-incubator/setup-miniconda@v2
+        with:
+          miniconda-version: "latest"
+          python-version: 3.8
+      - name: Create Conda Env
+        shell: bash -l {0}
+        run: |
+          conda clean --all --quiet --yes
+          CONDA_ENV="${RUNNER_TEMP}/conda_environment_${GITHUB_RUN_ID}"
+          conda create \
+            --yes \
+            --prefix "${CONDA_ENV}" \
+            "python=3.8"
+          echo "CONDA_ENV=${CONDA_ENV}" >> "${GITHUB_ENV}"
+          echo "CONDA_RUN=conda run -p ${CONDA_ENV}" >> "${GITHUB_ENV}"
+      - name: Run pydocstyle
+        shell: bash -l {0}
+        run: |
+          ${CONDA_RUN} pip install pydocstyle
+          ${CONDA_RUN} pydocstyle torchaudio