nvim: init treesiter-nvim

I wanted fancy markdown rendering in nvim and that needed a treesitter
lsp, so this adds treesitter and the markdown lsp.

config/nvim/nvim.lua

@@ -22,6 +22,14 @@ require'lspconfig'.pylsp.setup{
     }
   }
 }
+require'nvim-treesitter.configs'.setup {
+  ensure_installed = { },
+  auto_install = false,
+  highlight = {
+    enable = true,
+    additional_vim_regex_highlighting = false,
+  },
+}
 
 -- Add additional capabilities supported by nvim-cmp
 local capabilities = require("cmp_nvim_lsp").default_capabilities()

packages/default.nix

@@ -113,6 +113,11 @@ in
               neo-tree-nvim
               nvim-cmp
               nvim-lspconfig
+              (nvim-treesitter.withPlugins (
+                plugins: with plugins; [
+                  markdown
+                ]
+              ))
               spaceman-nvim
               telescope-nvim
               telescope-undo-nvim