OIS-49: Updated readme with alpine image note (#3)

Author: sradziszewski

README.md

@@ -2,7 +2,11 @@
 
 Image for launching (non-)interactive containers with gradle suitable for developing OpenLMIS v3+ Services.
 
-Based off of alpine-java.
+Currently the image is based on alpine-java version:  
+[![Docker Image Version (tag)](https://img.shields.io/docker/v/_/alpine/3.13)](https://hub.docker.com/layers/library/alpine/3.13/images/sha256-16fd981ddc557fd3b38209d15e7ee8e3e6d9d4d579655e8e47243e2c8525b503?context=explore)
+### Important Note:
+It is highly suggested to check the base image for vulnerabilities and update the version if necessary.
+
 
 ## Versions