[Feature] Support broadcast messages in http sub mode

[keranbingaa]

I have download the code and run the eventmesh with tcp/http mode, but i want to use broadcast mode in http, when i run more than one application in consumer group , only one application can receieve the message from the topic which they subscribe.

[xwm1992]

yes, eventmesh doesn't support broadcast messages in http sub mode yet. we will support this feature later or you can submit your code pull request for this feature, thanks