Add app id as name for launcher widget buttons

[ozmodeuz]

Is your feature request related to a problem? Please describe.
As a mechanism to allow styling of app icons/labels in the launcher on a per-app basis.

Describe the solution you'd like
Set the given app id as the corresponding button widget's name, per this comment.

Describe alternatives you've considered
Alternatively a way to pass the app id to an embedded script? But might still need the CSS selector to make good use of that.

[ozmodeuz]

My suggestion for the script side of things from the discussion, which I should've posted here 🙃

As for replacing the icon, I was thinking about the content property in CSS, but it looks like GTK 3's version of CSS doesn't implement that. Alternatively perhaps there could be an option for the launcher which sets the format of each app's name, and which accepts the app's ID as an input?

So you could have something like:

- type: launcher
  show_names: true
  show_icons: false
  name_format: {{script which outputs nerdfont for $app_id here}}