Suggestion: Add Tree View for File Navigation #21

Hi 👋,

First of all, thanks for this amazing project! I really enjoyed how rendergit flattens a GitHub repository into a single HTML file with all the contents accessible.

Currently, the left-hand Contents sidebar lists all files in a single flat structure. While this provides quick access, it becomes difficult to navigate in larger repositories because the directory hierarchy is lost, making it harder to understand the project’s organization at a glance.

Suggestion 1 : It would be very useful if the contents sidebar could display files in a tree format, mirroring the folder structure.
This would make navigation easier to relate to and more intuitive.

Suggestion 2 : Each file in the directory tree could also be a hyperlink directly to its section in the rendered HTML.