Document signal handler naming convention

doc/source/module_development.md

@@ -90,6 +90,7 @@ For the most part, use `clang-format` and follow Godot conventions.
 - Parameters prefixed with `p_`, but not really enforced so far. Matters for big functions.
 - Private and protected fields prefixed with `_`
 - Some private functions start with `_`, either to mimic Godot API, or if it's a re-used function that performs no checks
+- Signal handler functions are prefixed with `_on_` and should never be called manually
 - Enums prefixed by their name. Example: `enum Type { TYPE_ONE, TYPE_TWO }`
 - Open braces at the end of line, close them next line
 - Never omit braces