chore: Add notes/docs based on PR review

Author: bryantbiggs

README.md

@@ -27,6 +27,9 @@ module "vpc" {
 }
 ```
 
+> [!WARNING]
+> v6.x of the module still supports creating a VPC Flow Log within the root (VPC) module. However, this is deprecated behavior and will be removed in v7.0.0. Please use the [standalone flow log](https://github.com/terraform-aws-modules/terraform-aws-vpc/tree/master/modules/flow-log) module instead.
+
 ## External NAT Gateway IPs
 
 By default this module will provision new Elastic IPs for the VPC's NAT Gateways.
@@ -116,6 +119,20 @@ If you need private subnets that should have no Internet routing (in the sense o
 
 Since AWS Lambda functions allocate Elastic Network Interfaces in proportion to the traffic received ([read more](https://docs.aws.amazon.com/lambda/latest/dg/vpc.html)), it can be useful to allocate a large private subnet for such allocations, while keeping the traffic they generate entirely internal to the VPC.
 
+## Conditional creation
+
+Prior to Terraform 0.13, you were unable to specify `count` in a module block. If you wish to toggle the creation of the module's resources in an older (pre 0.13) version of Terraform, you can use the `create_vpc` argument.
+
+```hcl
+# This VPC will not be created
+module "vpc" {
+  source = "terraform-aws-modules/vpc/aws"
+
+  create_vpc = false
+  # ... omitted
+}
+```
+
 ## Public access to RDS instances
 
 Sometimes it is handy to have public access to RDS instances (it is not recommended for production) by specifying these arguments: