Add release instructions to README #999

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...	27m 22s
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...	47m 51s
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...	46m 3s
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...	41m 2s
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...	42m 5s
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 13s
	4h 4m 36s

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