Allow variable expansion in URI's for cross machine linking to files

Use case or problem

I can link to files outside of the vault using [pretty name](<file:///drive:\path to file\file.ext>). However, on different machines, the subdirectory where the file is located could be different, which breaks portability.

Proposed solution

Allow to define a variable on each machine (e.g. ${library_dir} ), and then use that in the uri like pretty name