Add CI for `EESSI-extend` #51

Job	Run time
eessi_container_script (help)	1m 50s
eessi_container_script (listrepos_default)	1m 16s
eessi_container_script (run)	1m 49s
eessi_container_script (resume)	3m 7s
eessi_container_script (container)	2m 2s
eessi_container_script (listrepos_custom)	1m 32s
eessi_container_script (shell)	2m 34s
	14m 10s

Provide feedback