Allow configuring the script filename casing rule

Defaults to "Auto", which detects the casing based on the
preference of the currently selected language (C# for example
prefers PascalCase whereas GDScript prefers snake_case).

core/object/script_language.h

@@ -193,6 +193,10 @@ public:
 
 class ScriptLanguage : public Object {
 	GDCLASS(ScriptLanguage, Object)
+
+protected:
+	static void _bind_methods();
+
 public:
 	virtual String get_name() const = 0;
 
@@ -224,6 +228,13 @@ public:
 		TEMPLATE_PROJECT
 	};
 
+	enum ScriptNameCasing {
+		SCRIPT_NAME_CASING_AUTO,
+		SCRIPT_NAME_CASING_PASCAL_CASE,
+		SCRIPT_NAME_CASING_SNAKE_CASE,
+		SCRIPT_NAME_CASING_KEBAB_CASE,
+	};
+
 	struct ScriptTemplate {
 		String inherit = "Object";
 		String name;
@@ -260,6 +271,7 @@ public:
 	virtual bool can_make_function() const { return true; }
 	virtual Error open_in_external_editor(const Ref<Script> &p_script, int p_line, int p_col) { return ERR_UNAVAILABLE; }
 	virtual bool overrides_external_editor() { return false; }
+	virtual ScriptNameCasing preferred_file_name_casing() const { return SCRIPT_NAME_CASING_SNAKE_CASE; }
 
 	// Keep enums in sync with:
 	// scene/gui/code_edit.h - CodeEdit::CodeCompletionKind
@@ -405,6 +417,8 @@ public:
 	virtual ~ScriptLanguage() {}
 };
 
+VARIANT_ENUM_CAST(ScriptLanguage::ScriptNameCasing);
+
 extern uint8_t script_encryption_key[32];
 
 class PlaceHolderScriptInstance : public ScriptInstance {