By default while using vscode live share it is hard to work on
skins and extensions of mediawiki using the core repo as a project
base, as extensions and skins are included in .gitignore files.
Configuration of the sharing behaviour is possible and documented at
https://docs.microsoft.com/en-us/visualstudio/liveshare/reference/security
The files added in this commit mean that by default:
- .gitignore files are treated in the default way for the system
meaning they are hidden, but accessible.
- core node_modules and vendor and shared and in the tree
- extensions and skins are shared and in the tree
Change-Id: I5e44483bcf09aa2fb6d568de1e0689a76ab7338a
