Create README.md (#3966)

model_cards/codegram/calbert-base-uncased/README.md

+---
+language: catalan
+---
+
+# CALBERT: a Catalan Language Model
+
+## Introduction
+
+CALBERT is an open-source language model for Catalan based on the ALBERT architecture. 
+
+It is now available on Hugging Face in its `base-uncased` version, and was pretrained on the [OSCAR dataset](https://traces1.inria.fr/oscar/).
+
+For further information or requests, please go to the [GitHub repository](https://github.com/codegram/calbert)
+
+## Pre-trained models
+
+| Model                               |  Arch.           | Training data                     |
+|-------------------------------------|------------------|-----------------------------------|
+| `codegram` / `calbert-base-uncased` |  Base (uncased)  | OSCAR (4.3 GB of text)            |
+
+
+## Authors 
+
+CALBERT was trained and evaluated by [Txus Bach](https://twitter.com/txustice), as part of [Codegram](https://www.codegram.com)'s applied research.
+