Add support for the Watchdog features

[jnorris-cs]

Feature: The component contains the built-in watchdog feature. Address #4694

Feature: The onError() callback will be called with two arguments. The first one will be an error object (as it was before the release 3+). A second argument is an object that contains two properties:

{String} phase: 'initialization'|'runtime' - Informs when the error has occurred (during the editor/context initialization or after the initialization).

{Boolean} willEditorRestart - When true, it means that the editor component will restart itself.

The willEditorRestart property will not appear when the error has occurred in the context feature.

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Additional information

I did not add support for the Context watchdog like the React adapter has. I need to understand Context watchdog better to support it.

I basically copied the changes to the react adapter to the vue adapter.

I bumped the major version of the adapter since react went from 2.x to 3.0 with same change.

I tried to follow the PR conventions as best as I understand them. Please let me know if I missed anything.

All the watchdog feature request in the project were closed as duplicates in favor of ckeditor/ckeditor5#4693 so that is why I linked an issue in a different project.

[coveralls]

Pull Request Test Coverage Report for Build 343

• 50 of 50 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 100.0%

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Totals
Change from base Build 333:	0.0%
Covered Lines:	73
Relevant Lines:	73

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💛 - Coveralls

[Reinmar]

Jaw drop :) That's a massive contribution 👏  Thank you!

[pomek]

@psmyrek, would you like to review these changes?

[psmyrek]

Hey @jnorris-cs! This is awesome, thank you for your contribution. Before merging this PR we would need also the ContextWatchdog support. Would you like to try out, or should we take over your work and finish this PR?

[jnorris-cs]

Hey @jnorris-cs! This is awesome, thank you for your contribution. Before merging this PR we would need also the ContextWatchdog support. Would you like to try out, or should we take over your work and finish this PR?

@psmyrek I dont have the time to work on the ContextWatchdog anytime soon, so I would appreciate it if you finish it up. That would be awesome.