docs: add template to provision docker image based workspaces on fly.io (#6526)

* add fly.io example

* fix: `fly_volume` does not allow using - in name.

fix: `fly_volume` does not allow using - in the name.

* fix: provider versions  and settings

* fix: valid `fly_app` name

* chore: ipv6 is not used

* fix: names

strangely `fly_volume` does not allow `-` and `fly_app` does not allow `_`.

* chore: update max RAM

* add fly-auth-api managed variables

* Update README.md

* improve setup flow

- user is not prompted in UI for default values
- org slug is best fetched via CLI

* add metadata

* add to starter templates

---------

Co-authored-by: Ben <me@bpmct.net>

examples/examples.go

@@ -32,6 +32,7 @@ var (
 	//go:embed templates/gcp-vm-container
 	//go:embed templates/gcp-windows
 	//go:embed templates/kubernetes
+	//go:embed templates/fly-docker-image
 	files embed.FS
 
 	exampleBasePath = "https://github.com/coder/coder/tree/main/examples/templates/"