Allow nested search

[Jetroid]

Provides the option to make a nested search if required.

[Birne94]

I originally had the same issue, but was able to resolve it by appending a trailing / to my search directory:

webp:
  enabled: true
  quality: 100
  regenerate: false

  img_dir:
    - '/images/'

The plugin already performs a recursive search, but only when the path ends with a slash (/images**/*.* vs /images/**/*.*):

for imgfile in Dir[imgdir_source + "**/*.*"]