Support resource-specific content in templated sections

[kadamwhite]

As noted in #47, not all resources for which we generate the docs using a template are really comparable. Some require authentication, others require contextual overrides for things like the improperly named resources introduced by Gutenberg in order to be legible. We don't have a good way to support introducing these per-resource changes short of manually editing the generated files, which is not sustainable. We should come up with an alternative or more powerful templating solution, ideally.