fix(render): ensure buffer is modifiable before rendering

Author: soifou

lua/treesitter-context/render.lua

@@ -312,7 +312,9 @@ local function set_lines(bufnr, lines)
   end
 
   if redraw then
+    vim.bo[bufnr].modifiable = true
     api.nvim_buf_set_lines(bufnr, 0, -1, false, lines)
+    vim.bo[bufnr].modifiable = false
     vim.bo[bufnr].modified = false
   end