Reduce noise from shields-ci and shields-deployment bots

[tooomm]

The shields-ci bot (danger) currently says thank you in every PR, to all kind of contributors.
Maybe reduce that the new contributors only (if possible). It would be more helpful if it provides some useful link or hint in a way to those first timers.

The other hints like doc updates or warnings are fine I think.

See #1822 (comment)

Also, from #1826 (comment)

We may also want to disable the shields-deployment [bot] status info (for dependabot update PR's).

👍 Addressed in #1924

[chris48s]

This should be sorted now #1843 and #1924 are merged

[tooomm]

While #1843 stops danger from running on dependabot PR's (👍), it doesn't deal with

The shields-ci bot (danger) currently says thank you in every PR, to all kind of contributors.
Maybe reduce that the new contributors only (if possible). It would be more helpful if it provides some useful link or hint in a way to those first timers.

After thinking about it a bit more it's ok to have the bot reserve the first comment slot for potential edits and helpful hints with the thank you message.

But could the message be different for first timers to include some helpful links maybe?
"✨ Thanks for your first contribution to Shields, @tooomm!"
"Please have a look at our CONTRIBUTING hints and don't hesitate to ask questions at Discord."

and for others:
"✨ Thanks for your continuous (repeated?) contribution to Shields, @tooomm!"

A bit different idea 😄:
There could also be some gamification, if we check the commit count for example and show nicer, special messages to people who contribute more.

[chris48s]

I'm not sure off the top of my head how to efficiently work out if the user submitting the PR has previously contributed to the repository or not (when I say "efficiently", I mean using either the data provided by danger in the danger.github object or one additional GitHub API call), but I'm sure it is do-able. If anyone wants to pick this up, this probot integration https://github.com/behaviorbot/new-pr-welcome does it, so the code for that probably contains the answer to that question.