chore(package): remove sourcemaps from npm

[sapphi-red]

v4 has 4 times larger file size than v3 (v4: 716kB, v3: 168kB, packagephobia). Although it does not affect the final bundle size of app's using this package, I think smaller is better for file disk usage and install times.

This is because of a) sourcemap is now published and b) ESM support which doubles the files.

This PR removes sourcemaps from npm by the same approach with inikulin/parse5#516.
This reduces the package size to 295 kB. (-58.8%)

Since this package uses typescript (that doesn't have ugly outputs) and doesn't run minify, I think the output is readable without sourcemaps and can be removed. Also it seems there are some problems with Webpack (#785).

This PR completely removes sourcemaps. But because most of the size is coming from lib/generated/*.map, an alternative approach is to remove only them. (I think these sourcemaps are not much important because it's a generated code.)
This way the package size will be 328 kB.

diff for the alternative approach

• remove files field from package.json
• add the following .npmignore

  **/*
  !lib/**/*
  lib/generated/*.map
  lib/esm/generated/*.map
  

[fb55]

I removed source maps from parse5 because I couldn't figure out how to make them be valid, without checking in the original source code. entities works around that by linking to the source files hosted on GitHub.

I don't see a reason not to add them, as they can help users and don't take up too much space. Hope that makes sense!

[fb55]

About removing them for generated content: Definitely a better option, but I still don't see the need for this. If you want to save all the bytes, one of the online bundlers (esm.sh etc) will do so happily.

[sapphi-red]

It's kind of my personal preference, so I understand. Thanks for taking a look!