Post description of Replay PR to HN

[francescobrivio]

Following discussion at the AlCaDB Workshop (Tier0 contribution), I have a suggestion to improve Replays bookkeeping.

Since more users are going to be able to trigger replays it might be useful to add a functionality that
automatically posts the PR description to the HN, for documentation purposes.
@drkovalskyi correctly pointed out that not all the replays should be posted to HN as
some of them are purely technical or for internal testing/validation.

So a possible solution would be:

• Every time a PR is made the bot checks if the title contains the word Replay
  • If yes, the bot would post a message like:
    "If you want me to post the description of this Replay to the HN just press here."
    similar to what is done in CMSSW (see e.g. Build CMSSW_12_1_0_pre3 cms-sw/cmssw#35301 (comment))
  • If no, no further action is required