Optimize webpack config

[OlegWock]

GitHub Issue (if applicable): n/a

I optimized webpack config a bit (without changing output format) and also updated all related loaders. This cut webpack compilation time in ~half on my machine, which in pair with added yarn watch:webpack allows to iterate a lot quicker, without waiting for full build process after each change.

Time changes on my machine

(With preinstalled dependencies)

Before optimizations:

❯ yarn build:development
...
✨  Done in 9.89s.

❯ yarn build:production
...
✨  Done in 13.69s.

After optimizations:

❯ yarn build:development
...
✨  Done in 6.40s.

❯ yarn build:production
...
✨  Done in 8.93s.

(Difference isn't 2x because I only optimized webpack part of pipeline, index generators were kept intact)