direnv.nix: init, move direnv to own file

modules/programs/other/direnv.nix

@@ -0,0 +1,15 @@
+_: {
+  programs.direnv = {
+    enable = true;
+    # PLEASE BE SILENT
+    silent = true;
+
+    # We want direnv to load in our nix dev shells
+    loadInNixShell = true;
+
+    # Integrations for all our shells
+    enableZshIntegration = true;
+    enableFishIntegration = true;
+    enableBashIntegration = true;
+  };
+}

modules/programs/other/module.nix

@@ -0,0 +1,3 @@
+_: {
+  imports = [./direnv.nix];
+}