Howdy,

This is part of a multi-commit PR for leftwm/leftwm, leftwm/leftwm-theme, and leftwm/leftwm-community-themes.

The new utility will allow for easier installation of themes per leftwm/leftwm#27. The currently developed commands are as follows:

SUBCOMMANDS:
    add       downloads a theme
    help      Prints this message or the help of the given subcommand(s)
    list      lists installed LeftWM themes
    new       creates a new theme
    remove    removes an installed LeftWM theme
    search    fetches a list of LeftWM themes and searches for new ones
    set       sets your current theme and restarts LeftWM
    update    fetches updates to all themes

If I want to install the Coffee theme for example, I need to run the following:

leftwm-theme update
leftwm-theme add "Coffee"
leftwm-theme set "Coffee"

I'm sure the files could be better organized, and I trust someone will help with that. A few other commands were mentioned in leftwm/leftwm#27 that I'd like to get to, including next and the one mentioned in leftwm/leftwm#191 which is leftwm-theme check and leftwm-check.

Currently, the installer does not check if a theme is valid, it operates under the assumption that only files in known.toml will make it in, locked at a particular commit, so we know they're good. That would be a good next step I think.

Best,
Mautamu