Add "Open in Docker Dev Environments" links (#280)

* readme: add devenvs links in READMEs

Signed-off-by: Nick Sieger <nick@nicksieger.com>

spring-postgres/README.md

@@ -1,4 +1,11 @@
 ## Compose sample application
+
+### Use with Docker Development Environments
+
+You can open this sample in the Dev Environments feature of Docker Desktop version 4.12 or later.
+
+[Open in Docker Dev Environments <img src="../open_in_new.svg" alt="Open in Docker Dev Environments" align="top"/>](https://open.docker.com/dashboard/dev-envs?url=https://github.com/docker/awesome-compose/tree/master/spring-postgres)
+
 ### Java application with Spring framework and a Postgres database
 
 Project structure:
@@ -77,11 +84,3 @@ Removing spring-postgres_db_1      ... done
 Removing spring-postgres_backend_1 ... done
 Removing network spring-postgres_default
 ```
-
-## Use with Docker Development Environments
-
-You can use this sample with the Dev Environments feature of Docker Desktop.  
-To develop directly frontend or the backend services inside containers, you just need to use the https git url of the sample:  
-`https://github.com/docker/awesome-compose/tree/master/spring-postgres`
-
-![page](../dev-envs.png)