Fix typos in code and docs with codespell

Using v1.11.0 from https://github.com/lucasdemarchi/codespell

modules/gdscript/gdscript_parser.cpp

@@ -458,8 +458,8 @@ GDScriptParser::Node *GDScriptParser::_parse_expression(Node *p_parent, bool p_s
 			if (!validating) {
 
 				//this can be too slow for just validating code
-				if (for_completion && ScriptCodeCompletionCache::get_sigleton()) {
-					res = ScriptCodeCompletionCache::get_sigleton()->get_cached_resource(path);
+				if (for_completion && ScriptCodeCompletionCache::get_singleton()) {
+					res = ScriptCodeCompletionCache::get_singleton()->get_cached_resource(path);
 				} else {
 					res = ResourceLoader::load(path);
 				}