expandGlob: support an ignore permission denied option

[lowlighter]

Is your feature request related to a problem? Please describe.

Currently if you encounter an error due to os permission, if make the whole walk stop.

error: Uncaught (in promise) PermissionDenied: Permission denied (os error 13): readdir '/snap/core20/2379/etc/ssl/private'
  for await (const entry of Deno.readDir(root)) {

An option to "skip" permission denied files would be nice

Describe the solution you'd like

A new option

Describe alternatives you've considered