FEAT: Link to other PRs in flight

[gundalow]

In an effort to:

• Reduce duplicate issues & PRs
• Get extra eyes on PRs

I think it may be useful to use Ansibullbot to point people at existing PRs in flight.

For example:

"Thanks for this Issue/PR on lineinfile
There may be some existing PRs in flight that address this issue
If you visit https://ansible.sivel.net/pr/byfile.html and search for lineinfile you may find something of interested.
If that search doesn't return anything try searching for the topic files

Reviews on those PRs would be very welcome.

Thank you for your interest in Ansible

"

The PRs and issues open vary over time I'm not sure if we want the bot to add in a list of issues or link to a page which is (reasonably) uptodate.