Support native iOS crashes

[bruno-garcia]

PLCrashReporter is built-in but requires opt-in. We want to consider adding sentry-cocoa to get the other features.

[bitsandfoxes]

I think #254 takes care of this?
Should we consider reading the player-settings to avoid conflicts?

[bruno-garcia]

We can close this but reading the description this made me realize we should add to the docs:

"Sentry will already include a crash reporter for iOS. That means there's no need to use the Unity built-in crash reporting functionality https://docs.unity3d.com/ScriptReference/CrashReport.html "

Or something like that

[bitsandfoxes]

Added it to the docs: getsentry/sentry-docs#4069