feat(core) - track custom analytics events

[chrismclarke]

Is your feature request related to a problem? Please describe.
University team said that they would like to be able to track how many people have been playing the videos and how many people have opened resources.

Describe the solution you'd like
Use the existing google analytics integration to track video playback and resource open events as custom analytics events. Ideally this will be done by adding methods to the existing analytics service libs\shared\src\services\core\analytics.service.ts to track custom events, and the service called as required from video player and resource service.

Additional context
Documentation for firebase analytics used in the platform can be found at:
https://firebase.google.com/docs/analytics

Code for the video player can be found at libs\shared\src\features\video-player

Code for resource open can be found at apps\picsa-tools\resources-tool\src\app\services\resources-tool.service.ts