lint-staged & husky in monorepos

[nikzaugg]

This pull request explained:

• husky & lint-staged never worked correctly with our setup, nothing was formatted each time we committed. Even tough the pre-commit hook was fired it did not recognize any staged files.
• best practice is to remove husky from the sub-repos and only install it at the top-level
• this PR adds lerna https://github.com/lerna/lerna, the Nr. 1 tool to manage monorepos
• lerna can call npm scripts in sub-repos simultaneously
• the lerna.json holds some minor configs, most importantly the "packages":[ ... ], that tell where our repos are
• added a top-level package.json with the husky hook pre-commit, which will then run the pre-commit command in each sub-repo
• basically: if this is merged, then each time something is commited, the pre-commit script of every sub-repo is run

[alexscheitlin]

Nice one, I didn't know that.