[CASCON] Prepare slides for the workshop

[dhmlau]

Originated from #3692

For details, see: #3692 (comment). Cross posting the outline from that comment:

Outline

• Intro: 15 mins (I am comparing with the meetup talk, and feel we at least need 15 mins to get attendee familiar with the framework and understand what they will build.)
• Scaffold greeter app and plugin greet service: 20 mins
• Support different languages: 20 mins
• Enable the caching with sweeping for REST requests: 20 mins
• Configure the app and greeters: 20mins
• Q & A: 10 mins

Acceptance Criteria

• Create slides to highlight the concepts and technologies we touched in the tutorial

[dhmlau]

Closing as done.
@agnes512, could you please commit the slides to the repo? thanks! https://github.com/strongloop/cascon2019