Replace Symfony Exception Handler with Spatie Ignition

[AliceKLWilliams]

What does this implement/fix? Explain your changes.

Replaces the Symfony Exception Handler with the Spatie Ignition package - https://github.com/spatie/ignition. This provides a nicer debugging experience as the error page can show you the code in which the error was thrown, for example in this image from their Github repo:

Does this close any currently open issues?

https://github.com/Rareloop/lumberjack-core/issues/32 - This issue requested we move to the Laravel exception handler (which at the time was Whoops), but Laravel have now moved to use Spatie Ignition.

https://github.com/Rareloop/lumberjack-core/issues/54 - This PR replaces the Symfony exception handler, so these deprecation errors will no longer appear.

Any other comments?

Some of the work on https://github.com/Rareloop/lumberjack-core/pull/52 will no longer be required, as the error handler has been replaced

[corneflikweert]

@AliceKLWilliams @adamtomat Is there a possibility that you merge these changes? :)

[tommitchelmore]

This is being implemented as part of 8.0 (#61)