`bootstrap_include` for resource jobs is internal knowledge

### Enhancement Proposal

Neither resource or template documentation:

https://checkbox.readthedocs.io/en/latest/reference/units/resource.html
https://checkbox.readthedocs.io/en/latest/reference/units/template.html

Mention `bootstrap_include`, without which no template will get evaluated.

Start with the resource and template reference pages linked in the issue and locate where resource jobs and template evaluation are explained. Document the role of bootstrap_include so readers understand its relevance to template evaluation, then verify both pages clearly cover it.

Written by the indexing model from the issue text.