calcurse: Add myself as maintainer

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

pkgs/applications/misc/calcurse/default.nix

···
     changelog = "https://git.calcurse.org/calcurse.git/plain/CHANGES.md?h=v${version}";
     license = licenses.bsd2;
     platforms = platforms.unix;
+    maintainers = [ maintainers.matthiasbeyer ];
   };
 }