Deploy function to knative, and define a good worflow for this

In the future, we will use this repo: https://github.com/Greenstand/treetracker-functions to deploy function to knative, so we need to define a workflow for this:
- People write function and run test to cover the code.
- Run command, or github action to deploy the function to knative

Start by reviewing the repository and the proposed function-test and Knative deployment workflow described in the issue. Define what contributors should run to test functions and how deployment should be performed, either through a command or GitHub Action; done means both steps are documented and reproducible.

Written by the indexing model from the issue text.