deps: use `@agilgur5/tsconfig` to simplify `tsconfig`

Summary

Simplify tsconfig.json by using my own tsconfig, @agilgur5/tsconfig.

this is my own tsconfig base built on top of @tsconfig/strictest
- as you can see, it just reduces all the non-type-checking related config that @tsconfig/strictest doesn't cover
TS doesn't yet support package exports for tsconfigs yet (https://github.com/microsoft/TypeScript/issues/48665), hence the longer path into the package
Relative paths in tsconfig bases are also relative within node_modules (https://github.com/microsoft/TypeScript/issues/29172), so have to repeat any relative paths here
- And due to this, I think it's better right now for build to extend the base here instead of the build tsconfig in @agilgur5/tsconfig
- I didn't fully think that one through when I made it tbh, though it still serves as a good example tsconfig
- Maybe that will be different in the future if TS changes or otherwise comes up with a solution to this (see the issue)