Added note on lack of language pack repo & to use the wiki

src/octoprint/templates/dialogs/settings/appearance.jinja2

@@ -51,6 +51,13 @@
         <h3>{{ _('Manage Language Packs...') }}</h3>
     </div>
     <div class="modal-body">
+        <p>
+            <strong>{{ _('There is currently no central repository for language packs like there is for plugins - any help to change that is appreciated!') }}</strong>
+        </p>
+        <p>
+            {{ _('Until a repository is available, please see <a href="%(url)s" target="_blank" >the wiki</a> for language packs provided by the community.', url = "https://github.com/foosel/OctoPrint/wiki#language-packs") }}
+        </p>
+
         <h4>{{ _('Available Language Packs') }}</h4>
 
         <div data-bind="visible: languagePacksAvailable()">