Add CI for `EESSI-extend` #53

Job	Run time
eessi_container_script (help)	1m 27s
eessi_container_script (shell)	2m 0s
eessi_container_script (listrepos_default)	2m 9s
eessi_container_script (listrepos_custom)	2m 29s
eessi_container_script (resume)	2m 43s
eessi_container_script (run)	3m 5s
eessi_container_script (container)	2m 26s
	16m 19s

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