Expected Behaviour

New feature: file-system watch mode will detect a change in a function handler folder and then automatically build/push/deploy the affected function.

This would be done via the existing OpenFaaS API meaning all backends are supported - faas-fargate, faas-swarm, faas-netes and openfaas-operator.

Similar things are done in entire projects such as skaffold from Google. I know Stefan @stefanprodan is a fan of this project. I believe Skaffold needs a Dockerfile in a set place, we can workaround this by using "faas-cli build --shrinkwrap" or maybe a combination of all of the above.

The basic idea is to allow a "watch" / auto-reloader experience for function development.

Thoughts?