Fix: indentation errors: add .editorconfig, health check, docs

doc/godotdev.txt

@@ -129,6 +129,29 @@ Optional C# support:
 - C# LSP server (csharp-ls or OmniSharp)
 - netcoredbg debugger
 
+==============================================================================
+INDENTATION                                             *godotdev-indent*
+
+Godot (both GDScript and C#) expects **spaces, 4 per indent**.
+If you use tabs, the LSP often reports this diagnostic:
+
+    Used tab character for indentation instead of space as used before in the file. [-1] [-1]
+
+To fix this, you should use an `.editorconfig` file. Godot, Neovim
+(via editorconfig plugins), VSCode, and Rider all respect this.
+
+Example `.editorconfig`:
+
+    [*.gd]
+    indent_style = space
+    indent_size = 4
+
+    [*.cs]
+    indent_style = space
+    indent_size = 4
+
+See also: `:checkhealth godotdev`
+
 ==============================================================================
 License                                           *godotdev-license*
 

doc/tags

@@ -2,6 +2,7 @@ godotdev	godotdev.txt	/*godotdev*
 godotdev-checkhealth	godotdev.txt	/*godotdev-checkhealth*
 godotdev-configuration	godotdev.txt	/*godotdev-configuration*
 godotdev-external	godotdev.txt	/*godotdev-external*
+godotdev-indent	godotdev.txt	/*godotdev-indent*
 godotdev-intro	godotdev.txt	/*godotdev-intro*
 godotdev-keymaps	godotdev.txt	/*godotdev-keymaps*
 godotdev-license	godotdev.txt	/*godotdev-license*