Add screen tracking plugin and add support for browser plugins

[matus-tomlein]

This PR adds a new screen tracking plugin for tracking screen view events. The plugin has full support for screen engagement tracking which means it has the following functionality:

1. Automatically tracks a screen_end event just before transitioning to a new screen view event.
2. Attaches a screen_summary context entity to screen_end, application_foreground and application_background events.

It also tracks the screen context entity with all events following a screen view and adds previousName and previousId references to screen view events.

The plugin is included in the React Native tracker. In order to make it compatible with the tracker, I had to add support for browser tracker plugins. By doing this, the tracker is now compatible also with our other browser plugins, such as the e-commerce plugin – I added unit tests for this.

[bundlemon]

BundleMon

Files added (6)

Status	Path	Size	Limits
✅	trackers/javascript-tracker/dist/sp.js	+24.54KB	30KB / +10%
✅	libraries/browser-tracker-core/dist/index.mod ule.js	+23.59KB	25KB / +10%
✅	libraries/tracker-core/dist/index.module.js	+19.5KB	20KB / +10%
✅	trackers/browser-tracker/dist/index.umd.min.j s	+17.44KB	20KB / +10%
✅	trackers/javascript-tracker/dist/sp.lite.js	+17.39KB	20KB / +10%
✅	trackers/browser-tracker/dist/index.module.js	+3.49KB	5KB / +10%

Total files change +105.95KB 0%

Final result: ✅

View report in BundleMon website ➡️

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Current branch size history

[mscwilson]

lgtm