build

README: add section on Upgrading #568

Job	Run time
Testing Node 18 on ubuntu-20.04	59s
Testing Node 20 on ubuntu-20.04	1m 1s
Testing Node 22 on ubuntu-20.04	1m 3s
Testing Node 23 on ubuntu-20.04	1m 2s
Testing Node 18 on macos-13	52s
Testing Node 20 on macos-13	1m 12s
Testing Node 22 on macos-13	50s
Testing Node 23 on macos-13	1m 25s
Testing Node 18 on macos-14	39s
Testing Node 20 on macos-14	34s
Testing Node 22 on macos-14	47s
Testing Node 23 on macos-14	45s
Testing Node 18 on windows-2019	2m 15s
Testing Node 20 on windows-2019	3m 18s
Testing Node 22 on windows-2019	3m 17s
Testing Node 23 on windows-2019	3m 7s
Prebuild on alpine (${{ matrix.arch }})	0s
Prebuild on alpine	0s
Prebuild on ${{ matrix.os }}	0s
Prebuild on Linux (${{ matrix.arch }})	0s
Publishing to NPM	0s
	23m 6s

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