Update lazy.nvim installation config (#129)

The current version of the config doesn't enable highlighting of Nushell
code.

ChatGPT suggested the changes. I tested the changes with a freshly
installed kickstart.nvim and NvChad, and they seem to be working for me.
However, I'm a total noob with nvim.

installation/neovim.md

@@ -8,10 +8,15 @@ Extend your lazy config with treesitter and the nu parser. The parser doesn't ha
 {
     "nvim-treesitter/nvim-treesitter",
     config = function()
-        -- setup treesitter with config
+        require("nvim-treesitter.configs").setup {
+            ensure_installed = { "nu" }, -- Ensure the "nu" parser is installed
+            highlight = {
+                enable = true,            -- Enable syntax highlighting
+            },
+        }
     end,
     dependencies = {
-        -- NOTE: additional parser
+        -- Additional Nushell parser
         { "nushell/tree-sitter-nu", build = ":TSUpdate nu" },
     },
     build = ":TSUpdate",