feat: button improvements

[w-lfchen]

Description

• supersedes Make onclick trigger for both mouse and keyboard #640 (that pr can be closed)
• buttons can be activated using the keyboard now
• if buttons play animations on click (catppuccin gtk theme for example), these are now played when they are right-/middleclicked as well
• buttons and eventboxes now consistently activate on key/button release
• some more cleanup in widget_definitions.rs

Usage

currently supported keys:

• space
• return/enter

Showcase

here's the config i tested with:

(defvar left 0)
(defvar mid 0)
(defvar right 0)
(defwindow example
  :monitor 0
  :focusable true
  :geometry (geometry
    :width "100%"
    :height "30px"
    :anchor "top center"
  )
  (button
    :onclick "eww update left=${left+1}"
    :onmiddleclick "eww update mid=${mid+1}"
    :onrightclick "eww update right=${right+1}; eww close example"
    "l: ${left}, m: ${mid}, r: ${right}"
  ))

Additional Notes

we could achieve a bit better performance if we don't want the fancy animation support.
i think the trade-off is worth it, but if you (the person reading this) think differently, feel free to comment. testing is also appreciated

⚠️ help wanted ⚠️

i've attempted to implement this logic for eventboxes as well and failed, i don't think this is possible for those, but i'm not sure.
i'd appreaciate it a lot if someone could investigate this further (in a new pr so that this one can be merged)

Checklist

• I added my changes to CHANGELOG.md, if appropriate.
• The documentation in the docs/content/main directory has been adjusted to reflect my changes.
• I used cargo fmt to automatically format all code before committing

[w-lfchen]

investigating some things