Improve npm package size

Have you read the FAQ and checked for duplicate open issues? Yes

Is your feature request related to a problem? Please describe. npm install shaka-player adds 22+Mb under node_modules. This is the entire content of the git repository plus the compiled JS files. I note that there is a .npmignore which is only omiting a few compilation artefacts.

Describe the solution you’d like Modify .npmignore to only include relevant dist files (e.g. demos aren’t presumably needed) and the sources needed for the .map files (lib, ui); this will reduce the disk size to about 8Mb.

Describe alternatives you’ve considered

Additional context

[elsassph]

I don’t think it should/needs to be possible to rebuild the project from the package. At least I’ve never done that for my packages…

For the externs - maybe there is a legitimate reason to keep them but I’m not familiar with it.

I’ve tried the change ony end (excluding .github as well as you noted) and can do a PR tomorrow.

[joeyparrish]

Sounds good. A PR would be appreciated. Thanks!