chore: fix github actions for build and release

[am29d]

During the build and release step we run tests to build the lambda layer. The layer is not pre-build and added to the git repo, like other layers from the CDK standard library. Instead, the layer is created during the synth step and thus needs access to docker runtime. But the node runtime does not have permission to docker during build and release process, thus we need to add this step to our workflow.

Sadly, the projen automatically generates the github workflow and actions and we can't add this modification (yet), so each npx projen build command will overwrite the workflow.

For now, I have generated the workflow from projen and deactivated the github integration. Once I know how to add this customisation, I will turn it back on.