[Idea] Add a flag to list templates

[SaxJ]

Hello!

I love this project, and have found it very useful, so thank you!

My idea is very simple, to add a --list-templates flag (or similar) to list templates. Just the name of each template on a line.

My use-case for this is making a user-interface in Emacs, and it would be useful to list templates so that they can fuzzy-selected fzf style.

If you think this idea is ok, I'd love to have a go implementing it. I've never used rust before and this feels like a nice intro.

Cheers!