Base URL documentation macro

[ibnishak]

Currently all links to official plugin demos are broken in offline version. See #6319

Suggested solution: A baseurl documentation macro referring to whether it is a pre-release or stable version. The macro can be concatenated with rest to url to derive correct links.

I am not familiar with the build script used by TW5. I am sure there are ways to correct the value of macro automatically on version bumps.

[Jermolene]

Hi @ibnishak I was thinking the macro would check for being on a file:// URI, and if so use the full URL, otherwise just use the relative one.