fix: Implement prettier

[Koenkk]

CC: @Nerivec

[Nerivec]

Well now, that's some cleanup job!

Probably should also enforce providing a reason for @ts-expect-error (ensure it's warranted).
Seems there are a lot of obj.hasOwnProperty('var') in here too, might want to change that to obj.var != undefined where appropriate (likely most of them).
Might want separate PRs though, to commit this faster to avoid too many conflicting PRs being opened in the meantime.