refactor(src): remove .js extension, append it for compiled files

[GervinFung]

I believe this thing is common, it's weird to import .js file when typescript files are imported/exported in src folder, and tsc should auto append the file extension for us, however, this problem can be solved with ts-add-js-extension. Do take a look at it and let me know what u think

[yaacovCR]

I agree 100% that it’s weird, but since we appear to be managing so far, I think we will probably avoid adding another dependency, at least for now.

Thanks for reaching out with your solution!