feat: language support via locale config (#96)

Co-authored-by: hiroki osame <hiroki.osame@gmail.com>

src/utils/config.ts

@@ -26,6 +26,12 @@ const configParsers = {
 
 		return key;
 	},
+	locale(key: string) {
+		parseAssert('locale', key, 'Cannot be empty');
+		parseAssert('locale', /^[a-z-]+$/i.test(key), 'Must be a valid locale (letters and dashes/underscores). You can consult the list of codes in: https://wikipedia.org/wiki/List_of_ISO_639-1_codes');
+
+		return key;
+	},
 	generate(key: string) {
 		parseAssert('generate', key, 'Cannot be empty');
 		parseAssert('generate', /^\d+$/.test(key), 'Must be an integer');