Add codeium and mundo to vim

Also: Expose packages in self#packagename for installation elsewhere on-system
Also: Reformat flake.nix
diff --git a/modules/neovim/undo/undo.vim b/modules/neovim/undo/undo.vim
new file mode 100644
index 0000000..73a30e7
--- /dev/null
+++ b/modules/neovim/undo/undo.vim
@@ -0,0 +1,4 @@
+set undofile
+set undodir=~/.config/nvim/undo
+
+nnoremap U :MundoToggle<CR>