Package proton into a tar.gz and extract on first-run

Valve requested that we distribute as few small files as possible, as
their content pipeline is very inefficient with small files.

toolmanifest.vdf

@@ -1,4 +1,4 @@
 "manifest"
 {
-  "commandline" "/bin/proton"
+  "commandline" "/proton"
 }