support gh-light-mode-only/gh-dark-mode-only tags in doxygen

Author: microdee

docs/Manual/index.md

@@ -2,7 +2,8 @@
 
 <div align="center">
 
-<img width="400px" src="nuke.cola.full.onDark.svg" />
+<img width="400px" src="nuke.cola.full.onLight.svg#gh-light-mode-only" />
+<img width="400px" src="nuke.cola.full.onDark.svg#gh-dark-mode-only" />
 
 Utilities and extensions useful for any [Nuke](https://nuke.build) builds originally separated from Nuke.Unreal.
 

docs/custom.css

@@ -1,3 +1,13 @@
 #projectalign {
     display: none;
-}
+}
+
+html.dark-mode img[src*="gh-light-mode-only"]
+{
+    display: none !important;
+}
+
+html.light-mode img[src*="gh-dark-mode-only"]
+{
+    display: none !important;
+}