New features and bugfixes

[FEATURE] Show registration in saveRegistrationResultAction #1136

Note, that there is a new argument for the saveRegistrationResultAction. Existing route enhancers should be adapted as following (new argument reguid):

-
  routePath: '/save-registration-result/{eventuid}/{reguid}/{result}/{hmac}'
  _controller: 'Event::saveRegistrationResult'
  _arguments:
    eventuid: eventuid
    reguid: reguid
    result: result
    hmac: hmac

[FEATURE] Added PSR-14 event to stop cancellation of depending registrations #1146
[FEATURE] Added ProceedWithPaymentActionEvent PSR-14 event #1139

[BUGFIX] Fix wrong invertStateDisplay for field hidden #1134
[BUGFIX] Respect DisableLanguageMenuProcessor in registration #1138
[BUGFIX] Fix deleteCustomNotificationsByEvent hook - #1140
[DOCS] Added linkhandler configuration #1135 - thanks @georgringer
[DOCS] Add link to documentation about breaking changes #1142
[DOCS] Fixed wrong TypoScript reference