Update the mtg arena installer and updater to be compatible with new mod.

.includes/magic-the-gathering-arena.sh

@@ -0,0 +1,10 @@
+#!/usr/bin/env bash
+
+run_mtga() {
+    local -a launchCommand=(wine)
+    if command -v gamemoderun >/dev/null; then
+        launchCommand=(gamemoderun wine)
+    fi
+cp "$cache/prism.dll" "$WINEPREFIX/drive_c/Program Files (x86)/Wizards of the Coast/MTGA"
+    "${launchCommand[@]}" "$@" &
+}