file path to source has hardcoded $HOME

By default, broot adds the following line to my rc file:

`source /Users/me/.config/broot/launcher/bash/br`

That works on my Mac, but on my Linux box my homedir is (obviously) different. How about instead making it:

`source $HOME/.config/broot/launcher/bash/br`

Inspect the broot code that generates the default shell rc-file line containing the hardcoded /Users/me/.config/broot/launcher/bash/br path. Check how the launcher path is selected for different platforms, then verify that the generated source line uses the user's home-directory variable and still works on macOS and Linux.

Written by the indexing model from the issue text.