AppRunner as an endpoint for Gobal Load Accelerator

**Tell us about your request**
AppRunner instances as an endpoint in Global Load Accelerator (GLA). Today, EC2 instances, ALB, NLB (among other endpoints) can be added to GLA to have it forward traffic from AWS edge locations to GLA endpoints wherever.

**Describe alternatives you've considered**
Alternatives include:
1. Spinning up Fargates behind an ALB / NLB / Edge-optimized APIGW
2. Multiple AppRunner domains ALIASd to a top-level Route53 managed, geo load-balanced domain.
3. Use Cloudflare to proxy requests to AppRunner endpoints (unsure if CloudFront can be used to same effect).
4. Open this issue and bide my time...

**Additional context**
Anything else we should know?
I am using Cloudflare right now, and paying them a hefty amount for a comparable setup.