Add support for aarch64 on Linux

[danberindei]

Since version 1.40.3, Deno releases include deno-aarch64-unknown-linux-gnu.zip.

asdf-deno doesn't install it because uname -m reports aarch64, but it worked fine with this change:

     case "$(uname -m)" in
       x86_64) architecture="x86_64" ;;
+      aarch64) architecture="aarch64" ;;