nvim: Enter notes dir when calling zettel index

When switching the current buffer to the Zettelkasten index page
(`<leader>ni`), we now also switch the working directory to the
corresponding notes directory.

nvim/.config/sh/alias.d/neovim.sh

@@ -0,0 +1,9 @@
+# v shorthand for neovim
+if exist nvim; then
+    alias v="nvim"
+    alias vim="nvim"
+
+    # open notes with my vim zettelkasten plugin
+    # TODO better implementation conditional on zk & zettelkasten existing
+    alias vn='nvim +"lua require \"zk.commands\".get(\"ZkCd\")()" +"lua require \"zettelkasten\".index_open()"'
+fi