improvements to bot success message

[ianstormtaylor]

Right now the success message looks like:

But I think it could be cleaned up and improved to look like:

With the addition that the table could be smartly collapsed only when the number of packages is greater than 10 (or whatever the right number is), so that in the simpler cases it can just always show.

Markdown for the example.

✅ Changeset detected. 2af1f4ff1932fe6b1c30984721b2e57ad647121e

The changes in this PR will be included in the next version bump.

Package	Type
slate	major	🔴
slate-history	patch	🟢
slate-hyperscript	minor	🟡
slate-react	patch	🟢
slate-test-utils	—	⚪️

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