Links to article source in a git system

[ftertre]

This is a functionnality available in Learn2 theme and really interresting when you are creating a documentation.

This PR add the possibility to have in the pages of the articles two links to Git management system (Github, Gitlab or other) to go directly on the source of the article for the first one (Edit this page) or to the history of commits for the second one (View history).

I have added two params in articles, one with the link to the tree, one with the link to the commits. If the parameter is missing in the config file, the link is not shown in the article.

It works for both single Grav site and multisite.

There is no request from other for that function, but as it was something needed for me, I share it ;)

[ftertre]

Forgot to say : I have made only English and French languages for the two texts needed by this PR (Edit this page and View history).

[Perlkonig]

Merci bien! I'll have to do some testing and then consider including it. I'll have to add some documentation.