improve order of session list

[CWempe]

I think the list of saved sessions should be ordered by name like in the Windows Explorer or VScode (or many other applications).

This means:

• case insensitive
• special characters like underscore should be listed above alphanumeric characters
• Folders above files (this already works as expected)

Currently the list in Kitty is case sensitive (bar is lower than Bar) and special characters at the beginning of a session name (_, -) seem to be getting ignored.

[pmatuszy]

correct - current setup is pretty not annoying but unnatural.