The XWiki Macro extension doesn't support escaping Macro attribute values

[vmassol]

Example inputs:

{{somemacro param1="val\"ue"/}}

{{somemacro param1="\value"/}}

{{somemacro param1='val\'ue'/}}

It would be great if that could be added since a lot of XWiki macros need to have attribute value content escaped in places.

I'd love to contribute a PR for this but I'm really not familiar with flexmark-java APIs (@vsch was really kind to write that module for us :)). Maybe with some guidance, I could have a try.