Enable `one-key-formatting` on new issue/PR title #4231

When creating a new issue, the one-key-formatting feature (i.e., select text, press `, ", etc. to wrap text with symbol) does not work on the body text or title text. You can try it when creating a new issue in this repo.

It also does not work in the title text for a new PR. Interestingly, it works fine in the PR body and elsewhere (e.g., comments)

https://user-images.githubusercontent.com/310197/114456843-344e2880-9b92-11eb-8d7d-35bfd5a199cf.mp4

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