Add the inbound.failed as a webhook event

[PeterOcansey]

resolves #https://github.com/mailersend/mailersend/issues/5743

Changelist

• [x] Add inbound_forward.failed event to webhook events params

[PeterOcansey]

@fosron I've added symfony/options-resolver as it is required by php-http/client-common

A wrong version for lower version of php causes this error with tests ParseError: syntax error, unexpected 'static' (T_STATIC)