* test: introduce tests
The aim of this change is to introduce the infrastructure so
that future contributors to the `functions` workspace can
be asked to include tests with minimal overhead.
A test has been added to demonstrate how functions triggered
by changes within the FireStore data can be validated.
If you want to run the tests locally you can do so using
the [firebase tools](https://www.npmjs.com/package/firebase-tools)
```bash
firebase emulators:exec --project default "jest ."
```
```bash
firebase emulators:exec --project default "jest . --watch"
```
* ci: downgrade jest to align with wider project
* feat: introduce tests
* chore: drop commit docs from this branch
* ci: reduce size of resouce class
* chore: align ts-jest with jest version
* docs: clarify wording for job
* fix: add jest types for functions
Co-authored-by: chrismclarke <chris.m.clarke@live.co.uk>
