contrib: add info about expectations and ping

[sylvestre]

No description provided.

[github-actions]

GNU testsuite comparison:

GNU test failed: tests/tail/follow-name. tests/tail/follow-name is passing on 'main'. Maybe you have to rebase?
Skipping an intermittent issue tests/tty/tty-eof (passes in this run but fails in the 'main' branch)

[codspeed-hq]

Merging this PR will improve performance by 4.82%

⚡ 1 improved benchmark
✅ 281 untouched benchmarks
⏩ 38 skipped benchmarks¹

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	Memory	du_wide_tree[(5000, 500)]	1.2 MB	1.2 MB	+4.82%

---

_{Comparing sylvestre:contrib (8febf5c) with main (c66be8c)}

Footnotes

1. 38 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩