Add bot messages for better status & communication

[craciunoiuc]

Right now the only message that the bot says is:

"This issue was closed by PR number "+fmt.Sprintf("#%d", ghPrId)+" which was merged successfully."

Ideally, it would additionally inform people that the merge is about to happen with x% of the tests passing for example.

On this front, logging can be also added to the application to verbosely detail each step that happens.

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Orthogonal to this, another idea would be to make a new command governctl pr bump that sends a message like This PR has been inactive for the past 28 days! and run that every month.

When a PR reaches 90 days from the last activity (push/comment/state change/merge) the label on the PR should be changed accordingly:

last change	status
<30 days	status/fresh
<60 days	status/stale
<90 days	status/rotten