Default checkbox in fieldset

[doneill]

Description

Fixes

#30

Proposed Changes

• Update getSchemaForCheckbox function
  • If not required: default to empty array
  • If required: no default (null is valid)

Testing

• Run yarn test
  • Verify all tests pass
• Build and link library in React Native app

# build
npm run build

# link
yarn link

# In React Native client app, e.g. EarthRanger
yarn remove @earthranger/react-native-jsonforms-formatter@2.0.0-beta.14
yarn link @earthranger/react-native-jsonforms-formatter@2.0.0-beta.17

[doneill]

Closing as library doesn't have access to the field component onChange handlers