chore: enable strict typescript checks

[43081j]

Enables most of what's in the unjs tsconfig template, plus the following:

• noUnusedLocals
• noUnusedParameters

i didn't take the entire unjs template because it'd mean changing the module/moduleResolution/moduleDetection

@pi0 almost all of the casts are because noUncheckedIndexedAccess is true. we can turn it off if you think we will do that quite often (e.g. when we check length of something, we know it then has [0] but typescript doesn't)

[pi0]

Thanks for your time on this. noUnusedLocals/noUnusedParameters are covered by eslint rules already btw and I agree noUncheckedIndexedAccess is sometimes little annoying with ts. Seems all good to me for now.