Update to (somewhat?) dendritic pattern

Heavily inspired by https://github.com/Doc-Steve/dendritic-design-with-flake-parts.

> Atomic commits? Never heard of them!

modules/programs/nixvim/_nixvim-config/keymaps.nix

@@ -0,0 +1,25 @@
+{ ... }: {
+  globals.mapleader = " ";
+
+  keymaps = [
+    {
+      key = "<esc>";
+      action = ":noh<CR>";
+      mode = "n";
+      options = {
+        silent = true;
+        desc = "Clear search highlight";
+      };
+    }
+    {
+      key = "j";
+      action = "gj";
+      mode = "n";
+    }
+    {
+      key = "k";
+      action = "gk";
+      mode = "n";
+    }
+  ];
+}