add toggle-window-rule-opacity action

[Faervan]

Add an action that toggles the opacity of the active window (or the window with the given id).

[phisch]

Could possibly be done if something like this was implemented: #1001

[Faervan]

Could possibly be done if something like this was implemented: #1001

well as I understand #1001 it would only allow to toggle a config block on or off. The point of this pr is to enable a per-window toggle of the opacity. The global opacity toggle can already be accomplished by making a custom script using sed (as YaLTeR pointed out on matrix) or smth similar, but a per-window toggle without this pr would require setting config rules for the focused window using the app-id and title, which would be a really hacky and ugly workaround I imagine.
This pr is a more elegant and 100% working solution to archive this.

[YaLTeR]

Did some small fixes, particularly when the opacity window rule becomes 1, the ignore flag is reset to avoid surprises later on. Let's merge this.

[YaLTeR]

Thanks!

[Faervan]

thank you for merging this :)