add and handle OpenWiki link action

osu.Game/Online/Chat/MessageFormatter.cs

@@ -167,6 +167,9 @@ namespace osu.Game.Online.Chat
                             case "u":
                             case "users":
                                 return new LinkDetails(LinkAction.OpenUserProfile, mainArg);
+
+                            case "wiki":
+                                return new LinkDetails(LinkAction.OpenWiki, string.Join('/', args.Skip(3)));
                         }
                     }
 
@@ -311,7 +314,8 @@ namespace osu.Game.Online.Chat
         JoinMultiplayerMatch,
         Spectate,
         OpenUserProfile,
-        Custom
+        OpenWiki,
+        Custom,
     }
 
     public class Link : IComparable<Link>

osu.Game/OsuGame.cs

@@ -309,6 +309,10 @@ namespace osu.Game
                         ShowUser(userId);
                     break;
 
+                case LinkAction.OpenWiki:
+                    ShowWiki(link.Argument);
+                    break;
+
                 default:
                     throw new NotImplementedException($"This {nameof(LinkAction)} ({link.Action.ToString()}) is missing an associated action.");
             }
@@ -356,6 +360,12 @@ namespace osu.Game
         /// <param name="beatmapId">The beatmap to show.</param>
         public void ShowBeatmap(int beatmapId) => waitForReady(() => beatmapSetOverlay, _ => beatmapSetOverlay.FetchAndShowBeatmap(beatmapId));
 
+        /// <summary>
+        /// Show a wiki's page as an overlay
+        /// </summary>
+        /// <param name="path">The wiki page to show</param>
+        public void ShowWiki(string path) => waitForReady(() => wikiOverlay, _ => wikiOverlay.ShowPage(path));
+
         /// <summary>
         /// Present a beatmap at song select immediately.
         /// The user should have already requested this interactively.