updated the main readme

readme.md

@@ -6,5 +6,6 @@ Each project is standalone and isolated into its own directory:
 
 | project | description |
 | --- | --- |
+| [4-hello-world-argon-base](./4-hello-world-argon-base/) | A hello world f# console application with argon as base image. |
 | [2-hello-world](./2-hello-world/) | A hello world f# console application. |
 | [1-markdown](./1-markdown/) | Render simple markdown into pdf and html using pandoc. |