[Feature] simple aws implement

[kevinten10]

I add a simple email message sending process.

core layor:

• email-core (https://github.com/reactivegroup/reactive-message-gateway/tree/master/rmg-email-core)
• email-core of aws (https://github.com/reactivegroup/reactive-message-gateway/tree/master/rmg-email-core-aws)

web api layor:

• webflux api of aws (https://github.com/reactivegroup/reactive-message-gateway/tree/master/rmg-email-interface-webflux-aws)
• rsocket api of aws (https://github.com/reactivegroup/reactive-message-gateway/tree/master/rmg-email-interface-rsocket-aws)

subscriber layor:

• subcriber of aws ses sdk (https://github.com/reactivegroup/reactive-message-gateway/tree/master/rmg-email-subscriber-aws)

they like:

webflux aws web api                                      
       ....               →   email core process  ->   email subscriber aws ses sdk 
rsocket aws web api