Add a rollback strategy

[franky47]

Versions 1.3.0 and 1.3.1 were deployed with a silently broken build (see parcel-bundler/parcel#4681), leading to an empty bundle being deployed. Version 1.2.1 has been rolled back manually, but some automation should be implemented to avoid this scenario.

In this case we need:

• To be able to detect the sanity of the generated bundle and fail the build if integration tests fail
• To store the validated built artifacts before upload, so they can be used for a later rollback

The rollback story would ideally have to be a one-command solution that runs Surge deployment on a previously built artifact (no build step).

[franky47]

Some ideas:

• At the beginning of the deployment workflow, fetch the current production bundle and store it as an artifact.
• Build the current bundle and also store it as an artifact
• Deploy the current bundle
• Add a triggerable action to rollback from an existing artifact ?