Migrate model card from transformers-repo

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Original file history: https://github.com/huggingface/transformers/commits/master/model_cards/Cinnamon/electra-small-japanese-generator/README.md

README.md

@@ -0,0 +1,18 @@
+---
+language: ja
+---
+## Japanese ELECTRA-small
+
+We provide a Japanese **ELECTRA-Small** model, as described in [ELECTRA: Pre-training Text Encoders as Discriminators Rather Than Generators](https://openreview.net/pdf?id=r1xMH1BtvB).
+
+Our pretraining process employs subword units derived from the [Japanese Wikipedia](https://dumps.wikimedia.org/jawiki/latest), using the [Byte-Pair Encoding](https://www.aclweb.org/anthology/P16-1162.pdf) method and building on an initial tokenization with [mecab-ipadic-NEologd](https://github.com/neologd/mecab-ipadic-neologd). For optimal performance, please take care to set your MeCab dictionary appropriately.
+
+```
+# ELECTRA-small generator usage
+
+from transformers import BertJapaneseTokenizer, ElectraForMaskedLM
+
+tokenizer = BertJapaneseTokenizer.from_pretrained('Cinnamon/electra-small-japanese-generator', mecab_kwargs={"mecab_option": "-d /usr/lib/x86_64-linux-gnu/mecab/dic/mecab-ipadic-neologd"})
+
+model = ElectraForMaskedLM.from_pretrained('Cinnamon/electra-small-japanese-generator')
+```