Adds documentation on manual span propogation #34

Job	Run time
Unit tests / Construct unit test matrix	3s
Benchmarks / Construct Benchmarks matrix	3s
Cxx interop / Construct Cxx interop matrix	3s
Soundness / API breakage check	48s
Soundness / Format check	33s
Soundness / Unacceptable language check	4s
Soundness / License headers check	5s
Soundness / Documentation check	1m 0s
Soundness / Shell check	32s
Soundness / YAML lint check	4s
Soundness / Broken symlinks check	4s
Soundness / Python lint check	5s
Unit tests / Unit tests / Linux (6.0)	42s
Unit tests / Unit tests / Linux (nightly-main)	49s
Unit tests / Unit tests / Linux (nightly-next)	48s
Unit tests / Unit tests / Linux (6.1)	45s
Unit tests / Unit tests / Linux (5.10)	38s
Cxx interop / Cxx interop / Linux (nightly-main)	49s
Cxx interop / Cxx interop / Linux (6.0)	45s
Cxx interop / Cxx interop / Linux (6.1)	46s
Cxx interop / Cxx interop / Linux (nightly-next)	50s
Cxx interop / Cxx interop / Linux (5.10)	39s
Benchmarks / Benchmarks / Linux (6.0)	2m 33s
Benchmarks / Benchmarks / Linux (nightly-next)	2m 28s
Benchmarks / Benchmarks / Linux (6.1)	1m 53s
Benchmarks / Benchmarks / Linux (5.10)	2m 9s
Benchmarks / Benchmarks / Linux (nightly-main)	2m 23s
	22m 21s

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