[JR] Bugfix/restore original container style on destroy

[joshua-econify]

Fix #103

Description

• if bugfix:
  • Explanation of the problems behavior & repro steps, the code culprit and the solution.

Writing some tests to familiarize with ad.js (+ bonus increase coverage) and came across:

    this.originalStyle = container.style;

    container.style.position = 'sticky';
    container.style.top = `${stickyOffset}px`;

https://github.com/Econify/ad.js/blob/master/src/plugins/Sticky.ts#L34

Understanding is original style is a reference to container.style so the next line that sets the value of container.style overwrites the original value to be preserved in this.originalStyle (used for restoration in .onDestroy -> .cleanUp). As is this means position and top if set are never restored to their original values onDestroy -> cleanUp.

PR Requirements

Before requesting review this criteria must be met:
Overall test coverage >= current master?

• Yes
• N.A.

Documentation included (if any behavioral changes)?

• Yes
• N.A.

Backwards compatibility (if breaking change)?

• Yes
• N.A.

Release

Will this pr trigger a release i.e. version in package.json has been bumped?

• Yes
• No

Screenshots

If U.I. component, include screenshots or video screen capture showing
behavior and responsive styling below.