Support VideoJS v8

[amclin]

When VideoJS v8 is used, unit tests fail to pass. See #1045

https://videojs.com/guides/videojs-7-to-8/

Things to investigate:

• [ ] Dropped IE 11 support
• [x] Deprecated use of videojs.extend()
• [x] Newly deprecated functions
• [ ] Old deprecated functions
• [x] Aria attributes
• [x] firstplay event

[amclin]

videojs.extend() is not being used. We're already using the extends keyword instead

[amclin]

None of the newly deprecated functions are used in this plugin

[amclin]

The following old deprecated functions might be used in unit tests:

• hasClass
• getAttributes

The following old deprecated methods are used in the plugin:

• plugin

[amclin]

The firstplay event is not used in this plugin

[amclin]

This plugin is not currently providing any logic around aria attributes