Migrate model card from transformers-repo

Read announcement at https://discuss.huggingface.co/t/announcement-all-model-cards-will-be-migrated-to-hf-co-model-repos/2755
Original file history: https://github.com/huggingface/transformers/commits/master/model_cards/huggingface/CodeBERTa-small-v1/README.md

README.md

@@ -0,0 +1,130 @@
+---
+language: code
+thumbnail: https://cdn-media.huggingface.co/CodeBERTa/CodeBERTa.png
+datasets:
+- code_search_net
+---
+
+# CodeBERTa
+
+CodeBERTa is a RoBERTa-like model trained on the [CodeSearchNet](https://github.blog/2019-09-26-introducing-the-codesearchnet-challenge/) dataset from GitHub.
+
+Supported languages:
+
+```shell
+"go"
+"java"
+"javascript"
+"php"
+"python"
+"ruby"
+```
+
+The **tokenizer** is a Byte-level BPE tokenizer trained on the corpus using Hugging Face `tokenizers`.
+
+Because it is trained on a corpus of code (vs. natural language), it encodes the corpus efficiently (the sequences are between 33% to 50% shorter, compared to the same corpus tokenized by gpt2/roberta).
+
+The (small) **model** is a 6-layer, 84M parameters, RoBERTa-like Transformer model – that’s the same number of layers & heads as DistilBERT – initialized from the default initialization settings and trained from scratch on the full corpus (~2M functions) for 5 epochs.
+
+### Tensorboard for this training ⤵️
+
+[![tb](https://cdn-media.huggingface.co/CodeBERTa/tensorboard.png)](https://tensorboard.dev/experiment/irRI7jXGQlqmlxXS0I07ew/#scalars)
+
+## Quick start: masked language modeling prediction
+
+```python
+PHP_CODE = """
+public static <mask> set(string $key, $value) {
+	if (!in_array($key, self::$allowedKeys)) {
+		throw new \InvalidArgumentException('Invalid key given');
+	}
+	self::$storedValues[$key] = $value;
+}
+""".lstrip()
+```
+
+### Does the model know how to complete simple PHP code?
+
+```python
+from transformers import pipeline
+
+fill_mask = pipeline(
+    "fill-mask",
+    model="huggingface/CodeBERTa-small-v1",
+    tokenizer="huggingface/CodeBERTa-small-v1"
+)
+
+fill_mask(PHP_CODE)
+
+## Top 5 predictions:
+# 
+' function' # prob 0.9999827146530151
+'function'  # 
+' void'     # 
+' def'      # 
+' final'    # 
+```
+
+### Yes! That was easy 🎉 What about some Python (warning: this is going to be meta)
+
+```python
+PYTHON_CODE = """
+def pipeline(
+    task: str,
+    model: Optional = None,
+    framework: Optional[<mask>] = None,
+    **kwargs
+) -> Pipeline:
+	pass
+""".lstrip()
+```
+
+Results:
+```python
+'framework', 'Framework', ' framework', 'None', 'str'
+```
+
+> This program can auto-complete itself! 😱
+
+### Just for fun, let's try to mask natural language (not code):
+
+```python
+fill_mask("My name is <mask>.")
+
+# {'sequence': '<s> My name is undefined.</s>', 'score': 0.2548016905784607, 'token': 3353}
+# {'sequence': '<s> My name is required.</s>', 'score': 0.07290805131196976, 'token': 2371}
+# {'sequence': '<s> My name is null.</s>', 'score': 0.06323737651109695, 'token': 469}
+# {'sequence': '<s> My name is name.</s>', 'score': 0.021919190883636475, 'token': 652}
+# {'sequence': '<s> My name is disabled.</s>', 'score': 0.019681859761476517, 'token': 7434}
+```
+
+This (kind of) works because code contains comments (which contain natural language).
+
+Of course, the most frequent name for a Computer scientist must be undefined 🤓.
+
+
+## Downstream task: [programming language identification](https://huggingface.co/huggingface/CodeBERTa-language-id)
+
+See the model card for **[`huggingface/CodeBERTa-language-id`](https://huggingface.co/huggingface/CodeBERTa-language-id)** 🤯.
+
+<br>
+
+## CodeSearchNet citation
+
+<details>
+
+```bibtex
+@article{husain_codesearchnet_2019,
+	title = {{CodeSearchNet} {Challenge}: {Evaluating} the {State} of {Semantic} {Code} {Search}},
+	shorttitle = {{CodeSearchNet} {Challenge}},
+	url = {http://arxiv.org/abs/1909.09436},
+	urldate = {2020-03-12},
+	journal = {arXiv:1909.09436 [cs, stat]},
+	author = {Husain, Hamel and Wu, Ho-Hsiang and Gazit, Tiferet and Allamanis, Miltiadis and Brockschmidt, Marc},
+	month = sep,
+	year = {2019},
+	note = {arXiv: 1909.09436},
+}
+```
+
+</details>