Add a playbook template for IICS documentation - INPLATFORM-88

Here's the IICS documentation repository content. I followed WSO2 EI documentation format as I thought it represents a really good format for on-boarding a new user, but we certainly can adjust that. Each md file has a TODO that we need to fill content.

@jont @JARED.KOSANOVIC @ERIC.SCHOVILLE @SHREYASH.SHRESTHA