[Feature request] Pull rake tasks into documentation

[ChrisBAshton]

A number of our repos have well-documented rake tasks of the form:

desc "Long description"
task :rake_task_name, %i[arg] => :environment |_task, arg|
  # do something
end

Here is an example.

These rake tasks are not indexed in the Developer Docs at all, unless reference to them has been duplicated in a repo's *.md documentation or on a dedicated Developer Docs page.

Given documentation tends to fall out of sync with code quite easily, it would be better to pull the actual real rake task descriptions into the Developer Docs, automatically. Then when we search "reslug person", it'll bring up the rake task rather than zero results.