added `.pre-commit-config.yaml` to the repo. To use it:

- `pip install pre-commit`
- Install the following Go packages:
  * go install github.com/go-critic/go-critic/cmd/gocritic@latest
  * go install https://pkg.go.dev/golang.org/x/tools/cmd/goimports@latest
  * go install golang.org/x/lint/golint@latest
- In your clone, run: `pre-commit install`

This will create .git/hooks/pre-commit and following that, these tests will run every time you invoke `git commit`:
```sh
go fmt...................................................................Passed
go imports...............................................................Passed
go vet...................................................................Passed
go lint..................................................................Passed
go-critic................................................................Passed
```