feature: add corner customization (closes #961) (#963)

## What are the changes about?

Add corner customization (what is in which corner of the screen)

## What existing issue does this resolve?

Issue #961

## Pre-requisites

- [x] I have tested & confirmed the changes work locally
- [x] I have run `zig fmt` throughout my changes

Co-authored-by: AnErrupTion <anerruption@disroot.org>
Reviewed-on: https://codeberg.org/fairyglade/ly/pulls/963
Reviewed-by: AnErrupTion <anerruption+codeberg@disroot.org>

res/config.ini

@@ -153,6 +153,34 @@ colormix_col2 = 0x000000FF
 # Color mixing animation third color id
 colormix_col3 = 0x20000000
 
+# Screen corners customization
+# Keywords:
+# keys     -> Power management keys (shutdown, restart, etc.)
+# clock    -> Clock (format defined by 'clock' option)
+# tty      -> Active TTY number
+# battery  -> Battery percentage
+# version  -> Ly version string
+# numlock  -> Numlock state
+# capslock -> Capslock state
+# labels   -> All custom info labels (lbl:)
+# binds    -> All custom keybind hints (cmd:)
+# lbl:name -> Specific custom info label
+# cmd:key  -> Specific custom keybind hint
+#
+# The order defines the vertical stack (first item is at the edge).
+
+# Bottom left
+corner_bottom_left = version
+
+# Bottom right
+corner_bottom_right = labels
+
+# Top left
+corner_top_left = keys
+
+# Top right
+corner_top_right = clock tty
+
 # For custom binds: the horizontal limit in characters for each
 # line of custom binds before moving on to the next.
 # If null, defaults to the width of the terminal instead.