Add Error Handler to Limit Exception Bubbling

[ProjectBarks]

The idea is to limit the scope in which exceptions in the injection code can break the react component. This reduces the risk of total app failure.

Added onError handler because passing new errors into afterInjection felt like I was overloading the function.

Example:
Before this would break your application, after the error is routed into onError and then defaulted to the fallback.

 <ReactSVG
        beforeInjection={() => {
          throw new Error('test error')
        }}
        fallback={fallback}
        src={`http://localhost/${uuid}.svg`}
      />

[ProjectBarks]

@tanem

[tanem]

Thanks for this PR @ProjectBarks. Sorry for the long delay, things got away on me a bit late last year 😅

Will have a look through the changes and will get back to you. Will bring the branch up-to-date etc, so there'll be some forced pushes ⚠️

[tanem]

Don't think we can get away with this as it's going to result in setState being called (L103) when the component is not mounted, which will throw an error. Will tweak things a bit.

[tanem]

Modified a few things and will merge now. Thanks for your contribution 🎉

[tanem]

Released in v16.0.0.