Fix typo in README.md
Fix typo in README.md

On line 96, change `modiledoc` to `mobiledoc`.
YoranBrondsema/mobiledoc-kit,mixonic/content-kit-editor,YoranBrondsema/mobiledoc-kit,bustlelabs/mobiledoc-kit,bustlelabs/content-kit-editor,bustlelabs/mobiledoc-kit,bustle/mobiledoc-kit,bustle/mobiledoc-kit,bustlelabs/content-kit-editor,YoranBrondsema/mobiledoc-kit,mixonic/content-kit-editor,mixonic/content-kit-editor,bustle/mobiledoc-kit,bustle/mobiledoc-kit,bustlelabs/mobiledoc-kit,bustlelabs/content-kit-editor