Add release instructions to README #1410

Job	Run time
build (4.2.7, ghcr.io/wtsi-npg/ub-16.04-irods-clients-4.2.7:latest, ghcr.io/wtsi-npg/ub-16.04-iro...	26m 52s
build (4.2.11, ghcr.io/wtsi-npg/ub-18.04-irods-clients-4.2.11:latest, ghcr.io/wtsi-npg/ub-18.04-i...	48m 19s
build (4.2.12, ghcr.io/wtsi-npg/ub-18.04-irods-clients-4.2.12:latest, ghcr.io/wtsi-npg/ub-18.04-i...	47m 23s
build (4.3.1, ghcr.io/wtsi-npg/ub-22.04-irods-clients-4.3.1:latest, ghcr.io/wtsi-npg/ub-22.04-iro...	43m 52s
build (4.3.2, ghcr.io/wtsi-npg/ub-22.04-irods-clients-4.3.2:latest, ghcr.io/wtsi-npg/ub-22.04-iro...	41m 0s
build (4.3.3, ghcr.io/wtsi-npg/ub-22.04-irods-clients-4.3.3:latest, ghcr.io/wtsi-npg/ub-22.04-iro...	40m 7s
	4h 7m 33s

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