Add initial config

Signed-off-by: Nikolaos Karaolidis <nick@karaolidis.com>

configs/neovim.nix

@@ -0,0 +1,8 @@
+{
+  programs.neovim = {
+    enable = true;
+    defaultEditor = true;
+    viAlias = true;
+    vimAlias = true;
+  };
+}