[Merged by Bors] - feat(CI): add emoji to maintainer merge'd PRs also

[grunweg]

The zulip bot reacts to all label changes, including arbitrary users setting that label. That seems harmless: the emoji is only informational, and the effect of false marking a PR with the label may simply be that it doesn't reviewed as well.

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This PR is cargo-culted, please review carefully.

[github-actions]

PR summary e2a5289bd7

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference

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Declarations diff

No declarations were harmed in the making of this PR! 🐙

You can run this locally as follows

## summary with just the declaration names:
./scripts/declarations_diff.sh <optional_commit>

## more verbose report:
./scripts/declarations_diff.sh long <optional_commit>

The doc-module for script/declarations_diff.sh contains some details about this script.

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No changes to technical debt.

You can run this locally as

./scripts/technical-debt-metrics.sh pr_summary

• The relative value is the weighted sum of the differences with weight given by the inverse of the current value of the statistic.
• The absolute value is the relative value divided by the total sum of the inverses of the current values (i.e. the weighted average of the differences).

[adomani]

This looks good to me!

Just one question: hammer is an "official" name for the emoji? If the emoji is a custom emoji, then I think that we should also track down some internal ID number, like for the closed PR emoji.

[grunweg]

Yes, 🔨 is an official emoji. See e.g here or try the signal messenger.

[grunweg]

I just pushed another commit, merging the two essentially duplicate workflows into one.

[adomani]

Thanks, I like the newer version, let's try it out!

bors merge

[mathlib-bors]

Pull request successfully merged into master.

Build succeeded:

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