MAINTAINERS: Add a "Pixel library" area

Add "Pixel library" area, which covers the newly introduced lib/pixel
and associated tests and samples.

Signed-off-by: Josuah Demangeon <me@josuah.net>

Author: josuah

MAINTAINERS.yml

@@ -3219,6 +3219,21 @@ PMCI:
   labels:
     - "area: PMCI"
 
+Pixel library:
+  status: maintained
+  maintainers:
+    - josuah
+  files:
+    - include/zephyr/pixel/
+    - lib/pixel/
+    - tests/lib/pixel/
+    - samples/lib/pixel/
+  labels:
+    - "area: Pixel Library"
+  tests:
+    - libraries.pixel
+  description: Library for pixel manipulation and image processing
+
 POSIX API layer:
   status: maintained
   maintainers: