Follow the exclude settings in `_config.yml`

[pilgrimlyieu]

Here's Include/Exclude file(s) setting in _config.yml. Can the searchdb generator follows this setting?

# Include / Exclude file(s)
## include:/exclude: options only apply to the 'source/' folder
include:
exclude:
  - "private_content/*"
ignore:

[pilgrimlyieu]

I've made some modification locally. If this feature can be taken into consideration, I would be very willing to open a PR.