fix: execute hook scripts with shebang shell

mentioned in commit e843ff4f

mentioned in merge request to-be-continuous/samples/mkdocs-on-s3!8 (merged)

mentioned in merge request kicker!46 (merged)

mentioned in merge request doc!13 (merged)

mentioned in merge request to-be-continuous/samples/mkdocs-on-s3!13 (merged)

mentioned in merge request kicker!92 (merged)

mentioned in merge request doc!19 (merged)

mentioned in merge request to-be-continuous/samples/angular-on-s3!81 (merged)

mentioned in merge request cedric3.olivier/mkdocs-on-s3!2 (closed)