Improve space-efficiency

[mintydev789]

The content on screen is not very space-efficient in some places currently. The following enhancements would help with this:

1. Explorer: reduce the left margin for each subsequent directory nesting to avoid so much wasted space. Perhaps the very first level of nesting isn't necessary at all if you only have one folder open in the workspace (which most people do, I believe).
2. Git repo: display the file name first and then the path to it in smaller font to avoid having to scroll (this is how it works in VS Code). Maybe reduce left margin before the checkboxes.
3. Reduce horizontal margin on the line numbers, according to the number of digits necessary for the currently open file (perhaps with a minimum of 3 digits so there's not too much variation). Relative line numbering should be considered too for this change.