Disable linting autocmd for readonly buffers

This should avoid linting in buffers outside of the user's control,
having in mind especially the handy LSP pop-ups that describe your
hovered symbol using markdown.

Co-authored-by: Robin Gruyters <2082795+rgruyters@users.noreply.github.com>

lua/kickstart/plugins/lint.lua

@@ -47,7 +47,9 @@ return {
       vim.api.nvim_create_autocmd({ 'BufEnter', 'BufWritePost', 'InsertLeave' }, {
         group = lint_augroup,
         callback = function()
-          lint.try_lint()
+          if vim.opt_local.modifiable:get() then
+            lint.try_lint()
+          end
         end,
       })
     end,