Add prettier formatting verification to CI

[JoshuaKGoldberg]

.js, .json, .md, .ts, .tsx, and .yml should all be Prettier-ed. And the Github Actions builds should verify it. 🧹

[fuadop]

@JoshuaKGoldberg about this, looks like prettier has to be set up from scratch for the repo ?

[fuadop]

Do you have a specific prettier config you love ?

[JoshuaKGoldberg]

I normally just go with the default settings. Though for accessibility (see: prettier/prettier#7475) I'm planning on switching all my repos to use tabs instead of spaces. So just that one setting difference: useTabs: true.

[fuadop]

Hey @JoshuaKGoldberg , I want to use the below configuration.. but the project codes (arrays, generics, etc.) .. don't follow the semi-colon rule.. which would make a whole lot of file change if I run prettier --write . . Is that okay ? or do I change the config to allow semi colon ?

{
  "trailingComma": "es5",
  "tabWidth": 4,
  "semi": false,
  "singleQuote": true,
  "useTabs": true
}

[JoshuaKGoldberg]

Oh! Forgive me, I'd forgotten whether semi is enabled or not. I strongly prefer semicolons.

[fuadop]

Yea I perfer semicolons too.

[fuadop]

How about the tabWidth ? Do you like it as four ? or two ?

[JoshuaKGoldberg]

Hmm, let's just go with the defaults.

[fuadop]

Okay ✅