Add l10n groups

[lukaszewczak]

Hi,

I would like to add list of all the current l10n groups for easy reference, as @obensource mention in #19 . Probably after audit process this list will shrink, but for this moment I think this will be a good point to reference all groups.

[Volem]

To help the audit initiative, can we include the main maintainer? A champion of that group kind of approach for each repo, so that we know who to contact. Does it make sense?

I take a look at the nodejs-tr repo for instance and it is passive for the last 2 years and I volunteer to be the main maintainer for it.

[Tiriel]

@Volem l like your idea, but I think that's a bit of the point of the audit, at least like we devised it. For now, having this list like this seems a good idea to me, and we can always add the champions with another PR when they all will be found.

For the PR itself: LGTM