Documenting custom icons

README.md

@@ -153,6 +153,37 @@ custom_keys:
     key: KEY_GUIDE
 ```
 
+## Custom icons
+
+You can customize any icon with a custom svg path using the `custom_icons`option. This is very useful when you want to add buttons for sources that doesn't have icons in MaterialDesign.
+
+Usage:
+
+```yaml
+custom_icons:
+  <button>: <svg_path>
+```
+
+Example:
+
+```yaml
+custom_icons:
+  hbo: >-
+    M7.042 16.896H4.414v-3.754H2.708v3.754H.01L0
+    7.22h2.708v3.6h1.706v-3.6h2.628zm12.043.046C21.795 16.94 24 14.689 24
+    11.978a4.89 4.89 0 0 0-4.915-4.92c-2.707-.002-4.09 1.991-4.432
+    2.795.003-1.207-1.187-2.632-2.58-2.634H7.59v9.674l4.181.001c1.686 0
+    2.886-1.46 2.888-2.713.385.788 1.72 2.762 4.427 2.76zm-7.665-3.936c.387 0
+    .692.382.692.817 0 .435-.305.817-.692.817h-1.33v-1.634zm.005-3.633c.387 0
+    .692.382.692.817 0 .436-.305.818-.692.818h-1.33V9.373zm1.77
+    2.607c.305-.039.813-.387.992-.61-.063.276-.068 1.074.006
+    1.35-.204-.314-.688-.701-.998-.74zm3.43 0a2.462 2.462 0 1 1 4.924 0 2.462
+    2.462 0 0 1-4.925 0zm2.462 1.936a1.936 1.936 0 1 0 0-3.872 1.936 1.936 0 0 0
+    0 3.872Z
+```
+
+The svg path was copied from [SimpleIcon](https://simpleicons.org/?q=hbo).
+
 ## Installation
 
 ### Step 1