add random password generation on user create/edit form (#123)

* Add button to generate password in UserEdit

* increase default random password length to 64, add more possible symbols to the generator

* update readme

src/i18n/index.d.ts

@@ -155,6 +155,7 @@ interface SynapseTranslationMessages extends TranslationMessages {
         erase_avatar: string;
         delete_media: string;
         redact_events: string;
+        generate_password: string;
       };
     };
     rooms: {