Add support for uploading audio attachments (#1630)

* Add support for audio attachments.
Partially addresses #1337

* Register Tusky as a target for audio sharing

* Use icon with textColorTertiary for audio preview

app/src/main/AndroidManifest.xml

@@ -89,6 +89,13 @@
 
                 <data android:mimeType="video/*" />
             </intent-filter>
+            <intent-filter>
+                <action android:name="android.intent.action.SEND" />
+
+                <category android:name="android.intent.category.DEFAULT" />
+
+                <data android:mimeType="audio/*" />
+            </intent-filter>
 
             <meta-data
                 android:name="android.service.chooser.chooser_target_service"