feat: add a skeleton of new data feeds endpoint

[fpdrozd]

This PR adds a new endpoint to the platform-sdk for managing the data feed settings.

Examples:

const response = await client.dataFeeds.list({
  bearer_token: '7381273269536713689562374856'
})

const response = await client.dataFeeds.create({
  bearer_token: '7381273269536713689562374856',
  data_feed_setting: {
    provider: 'google',
    name: 'Google data feed'
  }
})

This has to be tested once the spree api endpoint is functional.