New discussions are not included in `hasRichTextEditor`

[kidonng]

Prevents some features from working. I'm referring to the page creating a discussion, not when actually looking at one (which is already supported).

Example: https://refined-github.github.io/github-url-detection/?url=%2Fwithastro%2Froadmap%2Fdiscussions%2Fnew%3Fcategory%3Dproposal