Added support for Hotjar Events API.

[juliomalegria]

What does this PR do?

This PR adds track support for Hotjar integration script (Hotjar Events API).

Are there breaking changes in this PR?

No.

Testing

Testing completed successfully

  Hotjar Unit
    Constructing the integration
      ✓ should have the right settings
      ✓ should have the right settings with custom options
    #initialize
      ✓ should call this.ready() with valid options
      ✓ should prepare the needed globals
      ✓ should reject an invalid HJID
    after loading
      #identify
        ✓ should send id and traits
        ✓ should not send attributes when user is anonymous
      #track
        ✓ should send event and ignore properties
        ✓ should not send nameless event

HeadlessChrome 98.0.4758 (Mac OS X 10.15.7): Executed 9 of 9 SUCCESS (0.003 secs / 0.015 secs)
TOTAL: 9 SUCCESS

Any background context you want to provide?

Hotjar now has an Events API. It will be beneficial for Segment and Hotjar users to be able to make use of it seamlessly.

Is there parity with the server-side/android/iOS integration components (if applicable)?

No

Does this require a new integration setting? If so, please explain how the new setting works

No

Links to helpful docs and other external resources

https://help.hotjar.com/hc/en-us/articles/4405109971095-Events-API-Reference

[arielsilvestri]

LGTM!

[chrisradek]

@juliomalegria Thank you so much for the update and apologies for the delay in reviewing. This looks great, we'll merge it right away!

[chrisradek]

Merging into feature branch - will create new PR from feature branch to trigger CI.

Edit: PR to trigger CI - #677