Add docs/FORMATTER.md from Claro v1.17.26 zip

docs/FORMATTER.md

@@ -0,0 +1,25 @@
+# Claro Formatter
+
+Run:
+```bash
+claro fmt file.claro
+claro fmt file.claro --inplace
+```
+
+## What it does (Beta18)
+- Removes trailing whitespace
+- Normalizes indentation for common block structures:
+  - TEACH/LEARNED
+  - IF/ELSE/ENDIF
+  - FOR/DONE
+  - TRY/CATCH/ENDTRY
+  - DO/DONE
+  - REPEAT/UNTIL
+  - COMMENT/ENDCOMMENT
+
+Indentation step is 4 spaces.
+
+## What it does NOT do yet
+- Reflow long lines
+- Rename variables
+- Enforce style beyond indentation and whitespace