doc(pkg): Explain package management #28516

Job	Run time
Coverage (5.1.x)	9m 13s
Build microbenchmarks	2m 18s
Coq 8.16.1	7m 13s
Build (macos-latest, 5.1.x)	16m 42s
Build (ubuntu-latest, 5.1.x)	8m 41s
Create local opam switch (macos-latest, 5)	5m 20s
Documentation	52s
Build (ocaml-variants.5.3.0+trunk, ubuntu-latest, true)	5m 5s
Format	59s
Create local opam switch (macos-latest, 4.14)	5m 16s
Build (4.14.x, ubuntu-latest, true)	1m 34s
Create local opam switch (ubuntu-latest, 5)	4m 49s
Build (4.14.x, macos-latest, true)	2m 38s
Build monorepo benchmark docker image	1m 42s
Create local opam switch (ubuntu-latest, 4.14)	4m 51s
Nix (macos-latest)	1m 55s
Build (5.1.x, macos-13, true)	5m 44s
Nix (ubuntu-latest)	56s
Build (ocaml-base-compiler.4.14.2,system-msvc, windows-latest)	16m 22s
Build (ocaml-base-compiler.5.1.1,system-mingw, windows-latest)	10m 22s
Build (4.08.x, ubuntu-latest, true)	1m 33s
Build (4.04.x, ubuntu-latest, true, true)	4m 36s
Build (4.02.x, ubuntu-latest, true)	3m 58s
	2h 2m 39s

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