Testing presets docs

We should do an iteration on the [Preset authoring guide](https://github.com/godaddy/gasket/blob/main/packages/gasket-cli/docs/presets.md) and add some guidance for testing during development, such as a using the hidden [--preset-path](https://github.com/godaddy/gasket/blob/main/packages/gasket-cli/src/commands/create.js#L152-L159) flag with the **create** command.

