Changed my name from Stelpjo to my current name, Fußmatte

I also left a note for the in-game credits list to change the "ss" to an eszett when the Unicode font is implemented.

desktop_version/CONTRIBUTORS.txt

@@ -3,7 +3,7 @@ Contributors
 
 (Ordered alphabetically by last name.)
 
-* Matt "Stelpjo" Aaldenberg
+* Matt "Fußmatte" Aaldenberg
 * AlexApps99 (@AlexApps99)
 * Christoph Böhmwalder (@chrboe)
 * Charlie Bruce (@charliebruce)

desktop_version/src/Game.cpp

@@ -461,7 +461,7 @@ void Game::init(void)
 
     /* CONTRIBUTORS.txt, again listed alphabetically (according to `sort`) by last name */
     const char* githubfriends_arr[] = {
-    "Matt \"Stelpjo\" Aaldenberg",
+    "Matt \"Fussmatte\" Aaldenberg", // TODO: Change to "Fußmatte" if/when UTF-8 support is added
     "AlexApps99",
     "Christoph B{hmwalder",
     "Charlie Bruce",