Add pinterest domain and asset domains for link preview support

res/values/strings.xml

@@ -1180,7 +1180,7 @@
     <string name="preferences__pref_enter_sends_title">Enter key sends</string>
     <string name="preferences__pressing_the_enter_key_will_send_text_messages">Pressing the Enter key will send text messages</string>
     <string name="preferences__send_link_previews">Send link previews</string>
-    <string name="preferences__previews_are_supported_for">Previews are supported for Imgur, Instagram, Reddit, and YouTube links</string>
+    <string name="preferences__previews_are_supported_for">Previews are supported for Imgur, Instagram, Pinterest, Reddit, and YouTube links</string>
     <string name="preferences__choose_identity">Choose identity</string>
     <string name="preferences__choose_your_contact_entry_from_the_contacts_list">Choose your contact entry from the contacts list.</string>
     <string name="preferences__change_passphrase">Change passphrase</string>

src/org/thoughtcrime/securesms/linkpreview/LinkPreviewDomains.java

@@ -18,7 +18,10 @@ public class LinkPreviewDomains {
       "m.imgur.com",
       "instagram.com",
       "www.instagram.com",
-      "m.instagram.com"
+      "m.instagram.com",
+      "pinterest.com",
+      "www.pinterest.com",
+      "pin.it"
   ));
 
   public static final Set<String> IMAGES = new HashSet<>(Arrays.asList(
@@ -26,6 +29,7 @@ public class LinkPreviewDomains {
       "cdninstagram.com",
       "fbcdn.net",
       "redd.it",
-      "imgur.com"
+      "imgur.com",
+      "pinimg.com"
   ));
 }