Set first day of week

[fritz-net]

Since in most parts of the world the week does not start with sunday I implemented this.

[SteffoSpieler]

This pull request also includes the pull request for Support more than 5 colors. Also it adds the package-lock.json file, which isn't included in the repository currently. (I don't know if this is intended or not, I'm neither the maintainer, nor do I use this package actively myself.)

But appart from these, I'd love to see this merged.

[fritz-net]

@SteffoSpieler thanks for the review.
The other PR is included since I forked for this feature from my main and not the one in the original, totally missed that.

I would create a different branch and cherry pic the related changes if the Maintainer is willing to merge it in the first place. ( cherry picking resulted in merge conflicts since I changed the constructor in both PRs I think)

[fritz-net]

as far as I found out package-lock.json should be checked in:
https://stackoverflow.com/questions/44206782/do-i-commit-the-package-lock-json-file-created-by-npm-5