Fix Issue #282 by removing '.' from invalid characters list

This is actually a valid character name, at least in 2019, so I'm just
going to allow it for all versions. User beware (assuming it was actually
ever an illegal character at all).

Assets/RedBlueGames/MulliganRenamer/Editor/Renaming/RenamePreview.cs

@@ -109,7 +109,7 @@ public bool FinalNameContainsInvalidCharacters
                     return false;
                 }
 
-                var invalidCharacters = new char[] { '?', '.', '/', '<', '>', '\\', '|', '*', ':', '"' };
+                var invalidCharacters = new char[] { '?', '/', '<', '>', '\\', '|', '*', ':', '"' };
                 return this.RenameResultSequence.NewName.IndexOfAny(invalidCharacters) >= 0;
             }
         }