Fixed header on external tools doc

docs/tutorials/external.md

@@ -55,7 +55,7 @@ We have quite a few tutorials and many more in the works but the more the merrie
 [ :simple-steam: 'Godot4 - Deploy To SteamOS' by taw.moe](https://github.com/LauraWebdev/Godot4-DeployToSteamOS){ .md-button .md-button--resource target="\_blank" }
 
 {==
-C-Sharp Tools
+## C-Sharp Tools
 ==}
 
 [ :simple-godotengine: 'GodotSteam C# Bindings' by taw.moe](https://github.com/LauraWebdev/GodotSteam_CSharpBindings){ .md-button .md-button--resource target="\_blank" }