export environment env var for lf

This is useful when scripting lf and you need to adjust behavior for taolf. Eventually I will have to rewrite the opening mechanism to make a lot of this scripting easier.

lua/taolf/main.lua

@@ -116,7 +116,7 @@ function Lf:__set_cmd_wrapper()
     end
 
     self.term.cmd =
-        ([[%s -command='$printf $id > %s' -last-dir-path='%s' -selection-path='%s' '%s']])
+        ([[env TAOLF=true %s -command='$printf $id > %s' -last-dir-path='%s' -selection-path='%s' '%s']])
         :format(
             self.term.cmd,
             self.tmp_id,