esphome: add update script that includes the dashboard

pkgs/tools/misc/esphome/default.nix

···
 
   passthru = {
     dashboard = esphome-dashboard;
+    updateScript = callPackage ./update.nix {};
   };
 
   meta = with lib; {

pkgs/tools/misc/esphome/update.nix

···
+{ writeShellScript
+, lib
+, git
+, nix-update
+}:
+
+writeShellScript "update-esphome" ''
+  PATH=${lib.makeBinPath [ git nix-update ]}
+
+  nix-update esphome.dashboard
+  nix-update esphome
+''