add envelope dependency

Signed-off-by: Florian Brandes <florian.brandes@posteo.de>

devenv.nix

@@ -10,7 +10,7 @@
   # env.GREET = "devenv";
 
   # https://devenv.sh/packages/
-  # packages = [ pkgs.git ];
+  packages = [ pkgs.file ];
 
   # https://devenv.sh/scripts/
   # scripts.hello.exec = "echo hello from $GREET";
@@ -54,7 +54,6 @@
 
 
   };
-  # pre-commit.hooks.shellcheck.enable = true;
 
   # https://devenv.sh/processes/
   # processes.ping.exec = "ping example.com";

requirements.txt

@@ -1,2 +1,3 @@
 aiosmtpd
 aiosmtplib
+envelope