Update README.md

Author: Raycosine

glue/crumble/README.md

@@ -232,7 +232,7 @@ of the **Y gate** (y) (i.e. the gate `SQRT_YY_DAG 1 2`).
 - `ctrl++` or `ctrl+=`: Zoom in
 
 <a name="mouse-commands"></a>
-### Mouse Controls
+## Mouse Controls
 
 Note: to `BoxSelect` means to press down the left mouse button, drag the mouse
 while holding the button down to outline a rectangular region, and then release