fix: export types from build instead of src

[waaker]

@sberthier

Proposed change

Changed the way types are exported: index.d.ts now points to build directory instead of src in order to resolve to other .d.ts files in sub-directories instead of resolving to source .ts files.

Reason for change

I encountered a situation where a TS error in the source code of f-promise-async caused an error to be thrown at compile time when f-promise-async was included as a dependency.

According to microsoft/TypeScript#41883 (comment), inbound references should resolve to .d.ts files and not source .ts files.

The tsconfig skipLibCheck option can only affect the checking of .d.ts files. There are no options to avoid checking .ts files. Therefore, it is recommended to export types via .d.ts files, so that projects depending on this package can use skipLibCheck to choose if they want to perform the check, rather than being forced to do it.