WIP status-line-applet (rebased 2024-04-19)

[jokeyrhyme]

this is a rebase of #92

cc @ids1024 @ryanabx

• I do want to take some work from feat(i3status): new applet to embed i3status in panel/dock #344 before deleting it, but I don't intend for that PR/branch to sit around for longer than necessary
• I'll continue to add commits here and close 344

must-haves:

• launch a real i3status process and subscribe to its stdout
• parse the stdout lines into COSMIC widgets
• support both horizontal and vertical panels
• feed user clicks through to i3status process
• sort out error handling
• use the same font/size as the time/date applet

follow-up items (future PRs):

• provide a GUI for users to configure the font/size
• figure out what to do with pango-versus-nomarkup
• provide a GUI for users to set their own preferred command (e.g. a custom executable built with barista)
• applet icon

[jokeyrhyme]

much more reasonable font size now :)