Improved color bindings and support for all keywords of current i3 specifications.

[litoj]

Hello, I would like to contribute my additions to the syntax to support all keywords i3 has right now. I also notably changed color bindings to provide a more pg-language-like experience. More color links are used and newly I added a better highlighting conditions. This makes it possible for more colors to be used and people can distinguish more different functions.

[litoj]

The edits in README are mainly for myself, those were not supposed to go to the request, but I don't know how to remove a file from the request.

[hiqua]

Please consider making changes to the upstream vim repo directly as this code is there as of https://github.com/vim/vim/commit/8176be159859deb9cf6455565bd7b24b3dcf17b9

[hiqua]

@JosefLitos offer still stands to commit to the vim repo directly and make your changes available to everyone, including every other Arch Linux users.

[litoj]

I may give it a try soon, if all goes as planned.

[litoj]

@hiqua thanks for reminding me, should be ready to go, just made a couple more fixes: https://github.com/vim/vim/pull/10600