feat: Support sync message

[tienvx]

• This is for implementing compatibility suite
• Code (mostly) taken from this repository https://github.com/tienvx/pact-php-plugin
  • In the future I plan to move code from these repositories into this project also:
    • https://github.com/tienvx/pact-php-csv
    • https://github.com/tienvx/pact-php-protobuf
    • https://github.com/tienvx/pact-php-xml
  • It means most of the code will be in pact-php project. Outside of this project will be framework integration e.g. Symfony:
    • https://github.com/tienvx/pact-messenger-bundle
    • https://github.com/tienvx/pact-provider-bundle
• No test cases at all. This is because I'm not confident with the code structure yet.

[Lewiscowles1986]

👍