feat(twig-linter): Configuration (twigcs + grumphp) and fixes on the templates - TWIG-51

[planctus]

PR description

Basically i could not find a proper configuration in node to be able to lint twig files.
I've tried https://www.npmjs.com/package/eslint-config-twig but couldn't really get much out of that.
There is no plugin for prettier available yet, although this seems to be in the process, https://github.com/Kocal/prettier-plugin-twig

So i looked at solutions in the php world and we have a couple of "valid" linters there, i've added both:
https://github.com/asm89/twig-lint and https://github.com/friendsoftwig/twigcs.

I added documentation about the "sniffing" capabilities in the getting started file, you can follow that to see how this work, there's not much more than the default configuration.

Unfortunately for the time being the results are not so convincing, with one of the libraries we get no worries, with twig-cs we get 200 but most of the ones i checked were false positives.

QA Checklist

In order to ensure a safe and quick review, please check that your PR follow those guidelines:

• I have put the vanilla component as devDependencies
• I have put the specs package as devDependencies
• I have added the components directly used in the twig file (with include or embed) as dependencies
• My component is listed in @ecl-twig/ec-components's dependencies
• My variables naming follow the guidelines (snake case for twig)
• I have provided tests
• I have provided documentation (for the "notes" tab)
• If my local yarn.lock contains changes, I have committed it
• I have given my PR the proper label (pr: review needed to indicate that I'm done and now waiting for a review ,pr: wip to indicate that I'm actively working on it ...)

[drupol]

Nice !

Some feedback:

• I would not include composer.lock

[papegaill]

Nice! Tested, works like a charm.