Clarify reasons for disabling TS rules (and consider re-enabling some)

[axelboc]

Galex disables a lot of rules when TypeScript is enabled, to avoid reporting the same problems twice. This is mostly the case when:

• there's an equivalent rule in @typescript-eslint (e.g. @typescript-eslint/no-unused-vars,
• TypeScript reports the problem out of the box (e.g. no-undef); or thanks to built-in and external type definitions (e.g. react/no-invalid-html-attribute)

However, I've found a few cases where the reason for disabling the rule is unclear:

• import/no-deprecated (TS strikes those out in the IDE, but tsc does not warn about them, to my knowledge)
• import/no-duplicates ("Organize imports" does remove duplicate imports, but again, tsc does not report them)
• promise/catch-or-return (is this reported by TS somehow?)

In other cases, rules are disabled assuming (implicitly) that some configuration options are set in tsconfig.json:

• import/consistent-type-specifier-style (I think this relies on importsNotUsedAsValues being set to "error", right?)

I didn't have an exhaustive look through all the rules, so the lists may not be exhaustive. So it seems that some of them could be enabled, and for the rest, perhaps it would be good to always indicate a reason for disabling in the comments, like handled by @types/react, assumes "importsNotUsedAsValues": "error", etc.

[ljosberinn]

just wanna acknowledge the issue, quite busy atm but I haven't forgotten about this, thank you :)