[mac] Extract dock configuration to its own module.

Signed-off-by: jmug <u.g.a.mariano@gmail.com>

hosts/common/darwin/default.nix

@@ -0,0 +1,5 @@
+{ ... } : {
+  imports = [
+    ./dock.nix
+  ];
+}

hosts/common/darwin/dock.nix

@@ -0,0 +1,10 @@
+{ ... } : {
+  system.defaults.dock = {
+    autohide = true;
+    mru-spaces = false; # Don't reorder spaces.
+    show-recents = false; # Don't keep recent app icons around.
+    magnification= true;
+    tilesize = 48;
+    largesize= 96;
+  };
+}