feat(wm): add active window border

This commit adds an optional active window border with a user-defined
colour. This is achieved by spawning a dedicated "border window" and
constantly placing it behind the focused window, or hiding it whenever
necessary.

Some constraints to note:

- The border will only be applied to windows managed by komorebi
- This means that if you temporarily float a window, it will lose the
  active window border
- There are some issues where parts of the border will be broken by
  applications like Zoom, even if Zoom is behind the currently focused
  window
- You probably want to turn off window shadows globally in Advanced
  System Settings -> Performance for the borders to have a consistent
  colour all the way around the window
- There is some inevitable jank due to trying to reposition both the
  focused window and the "border window" behind it simultaneously
- There are no borders for unfocused windows

resolve #182

komorebic.lib.sample.ahk

@@ -300,6 +300,14 @@ IdentifyBorderOverflowApplication(identifier, id) {
     Run, komorebic.exe identify-border-overflow-application %identifier% "%id%", , Hide
 }
 
+ActiveWindowBorder(boolean_state) {
+    Run, komorebic.exe active-window-border %boolean_state%, , Hide
+}
+
+ActiveWindowBorderColour(r, g, b) {
+    Run, komorebic.exe active-window-border-colour %r% %g% %b%, , Hide
+}
+
 FocusFollowsMouse(boolean_state, implementation) {
     Run, komorebic.exe focus-follows-mouse %boolean_state% --implementation %implementation%, , Hide
 }