Feature: Integrated platform tips

[zfedoran]

This PR adds tipping support to the SDK.

The feature is still under internal testing/development on the mobile app and sequencer sides. Not ready to roll out yet.

Usage Example:

      const options = {
        mode: 'tip',
        platform: {
          name: 'twitter',
          username: 'getcode'
        }
      }

      const { button } = code.elements.create('button', options);

      button.on('error', (e) => { console.log('sdk-error', e); });
      button.on('cancel', (e) => { console.log('sdk-cancel', e); });

      button.mount("#my-button-container-id");