Update devcontainer.json

Added postCreateCommand setting. (This setting lets me run a custom command after creating the container.)

Author: Chau-Nguyen-Developer

.devcontainer/devcontainer.json

@@ -25,5 +25,7 @@
         "codespace.md"
       ]
     }
-  }
+  },
+
+  "postCreateCommand": "echo '# Writing code upon codespace creation!' >> codespace.md"
 }