feat: enforce AUTODEPLOY_TO_PROD and PUBLISH_ON_PROD as boolean variables

mentioned in commit 987c6e8f

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

mentioned in merge request to-be-continuous/samples/mkdocs-on-s3!14 (merged)

mentioned in merge request kicker!100 (merged)

mentioned in merge request doc!25 (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)