add(metadata): filter audible results by library language

static/index.html

@@ -30,6 +30,11 @@
             <option value="audiobook">Audiobook</option>
             <option value="comic">Comic/Manga</option>
           </select>
+          <select id="search-language" title="Nur Audiobooks: Sprache der Ausgabe">
+            <option value="">Alle Sprachen</option>
+            <option value="german">Deutsch</option>
+            <option value="english">Englisch</option>
+          </select>
           <input id="search-q" placeholder="Titel, Autor oder ISBN…" required />
           <button type="submit" id="search-btn">Suchen</button>
           <button type="button" id="manual-btn" class="secondary">
@@ -237,6 +242,7 @@
                 <th>Pfad</th>
                 <th>Ordner-Schema</th>
                 <th>Datei-Schema</th>
+                <th>Sprache</th>
                 <th></th>
               </tr>
             </thead>
@@ -267,6 +273,11 @@
             name="file_template"
             placeholder="Datei-Schema (optional)"
             class="wide" />
+          <select name="language" title="Sprache der Ausgaben in dieser Library — filtert die Audible-Suche">
+            <option value="">Sprache: egal</option>
+            <option value="german">Deutsch</option>
+            <option value="english">Englisch</option>
+          </select>
           <button type="submit" id="lib-form-submit">Anlegen</button>
           <button type="button" id="lib-form-cancel" class="secondary" hidden>
             Abbrechen