fix(file-templates): better recognize shell types

There are some conventional files strongly associated with a non-bash
shell which do not use an explicit `.zsh` file extension (e.g.
`.zprofile`); the old logic would always use the `#!/usr/bin/env bash`
shebang in these cases, which is a tiny little bummer.

modules/editor/file-templates/templates/sh-mode/__

@@ -1,3 +1,3 @@
-#!/usr/bin/env `(if (equal (file-name-extension buffer-file-name) "zsh") "zsh" "bash")`
+#!/usr/bin/env `(format "%s" sh-shell)`
 
 $0