ToDo: Create guidance for SLI calculation

[awsimaya]

Create a set of guidances to calculate SLIs for common use cases

Example

• Calculate Availability for these paths
  • API GW -> SQS -> Lambda
  • API GW -> Lambda -> DynamoDB
  • ELB -> EKS Pod -> RDS

Can think of other such use cases and SLIs to provide specific guidance for customers.