Make StringSchema.matches options optional

The second parameter to matches() should be optional. Giving it a default value, like the other methods, generates the appropriate optional types in the build.

src/string.ts

@@ -105,26 +105,24 @@ export default class StringSchema<
     });
   }
 
-  matches(regex: RegExp, options: MatchOptions | MatchOptions['message']) {
+  matches(regex: RegExp, options: MatchOptions | MatchOptions['message'] = locale.matches) {
     let excludeEmptyString = false;
     let message;
     let name;
 
-    if (options) {
-      if (typeof options === 'object') {
-        ({
-          excludeEmptyString = false,
-          message,
-          name,
-        } = options as MatchOptions);
-      } else {
-        message = options;
-      }
+    if (typeof options === 'object') {
+      ({
+        excludeEmptyString = false,
+        message,
+        name,
+      } = options as MatchOptions);
+    } else {
+      message = options;
     }
 
     return this.test({
       name: name || 'matches',
-      message: message || locale.matches,
+      message,
       params: { regex },
       test: (value: Maybe<string>) =>
         isAbsent(value) ||