mdbook-emojicodes: Add myself as maintainer

Signed-off-by: Matthias Beyer <[e-mail]>

pkgs/tools/text/mdbook-emojicodes/default.nix

···
     homepage = "https://github.com/blyxyas/mdbook-emojicodes";
     changelog = "https://github.com/blyxyas/mdbook-emojicodes/releases/tag/${version}";
     license = licenses.mit;
-    maintainers = with maintainers; [ blaggacao ];
+    maintainers = with maintainers; [ blaggacao matthiasbeyer ];
   };
 }