feat(wpcarro/emacs): Package maybe.el

(Temporarily) remove dependency on list.el in favor of dash, which I'm not
thrilled about.

Change-Id: Ic4348ee72582dee63ba07a183f3bda65baa7e2d6
Reviewed-on: https://cl.tvl.fyi/c/depot/+/5999
Reviewed-by: wpcarro <wpcarro@gmail.com>
Autosubmit: wpcarro <wpcarro@gmail.com>
Tested-by: BuildkiteCI

users/wpcarro/emacs/pkgs/maybe/default.nix

@@ -0,0 +1,24 @@
+{ pkgs, depot, ... }:
+
+let
+  maybe = pkgs.callPackage
+    ({ emacsPackages }:
+      emacsPackages.trivialBuild {
+        pname = "maybe";
+        version = "1.0.0";
+        src = ./maybe.el;
+        packageRequires = [ ];
+      })
+    { };
+
+  emacs = (pkgs.emacsPackagesFor pkgs.emacs28).emacsWithPackages (epkgs: [
+    maybe
+  ]);
+in
+maybe.overrideAttrs (_old: {
+  doCheck = true;
+  checkPhase = ''
+    ${emacs}/bin/emacs -batch \
+      -l ert -l ${./tests.el} -f ert-run-tests-batch-and-exit
+  '';
+})