Add some guesswork documentation for mumble link mapType.

Just going off the enum value names; in-depth investigation would probably
take at least a day to narrow down what all these are *actually* used for.
Pull requests based on empirical data are very much welcome! :D

mumble.md

@@ -32,4 +32,22 @@ struct MumbleContext {
     unsigned instance;
     unsigned buildId;
 };
+
+// mapType has some values roughly:
+// 0 = Redirect (e.g., when you log in while in a PvP match)
+// 1 = Character Create
+// 2 = Competitive PvP (probably unused)
+// 3 = GvG (lol unused ;_;)
+// 4 = Instance (probably dungeons/story content)
+// 5 = Public (probably general stuff)
+// 6 = Tournament (probably unused)
+// 7 = Tutorial (maybe unused?)
+// 8 = User Tournament (probably unused)
+// 9 = Eternal Battlegrounds
+// 10 = Blue Borderlands
+// 11 = Green Borderlands
+// 12 = Red Borderlands
+// 13 = Fortune's Vale (probably unused)
+// 14 = Obsidian Sanctum
+// 15 = Edge of the Mists
 ```