Relative path to workspace in title bar

[t-sauer]

Since a few days it seems to be possible to show the full path in the title bar in the insider builds.
This is already really helpful when figuring out where I am currently at in my codebase but most of the times the full path seems to be too much information in my opinion. A solution to this problem could be another option to only show the path starting from the workspace directory.

Example: I have a folder called my-app which is located in the folder ~/Development. When I open a file located in src/foo/bar/index.js for example, I can either display the full path (~/Development/my-app/src/foo/bar/index.js) or just the filename (index.js).
With the proposed addition the title could be reduced to src/foo/bar/index.js which in a lot of cases contains the information I am looking for when I look at the path of a file.

[bpasero]

Lets merge into #1723. If we provide full control of the title, the relative path could be one of the variables to pick from.