v0.5.0

• Added support for Socket Mode in a separate package: slack-php/slack-php-socket-mode.
• Removed SensitiveValue code and logic. Was unused by framework and not something we want to support externally.
• Added InputState helper class to assist in extracting submitted data from view_submission into a flat associative array structure and simplify the non-uniform input types.
• Fixed a bug in the Chain interceptor that was preventing interceptors from firing more than once in Socket Mode.
• Added the Base listener, which is an improvement on Dual listener.
• Deprecated the Dual listener (should use Base listener now).
• Fixed a bug in the WIP listener.