re-arrange the user docs (#76)

* re-arrange the user docs

* Minor description edit

* update styles

* fix service links

Co-authored-by: kn0wmad <kn0wmad@protonmail.com>
Co-authored-by: Lucy Cifferello <12953208+elvece@users.noreply.github.com>

site/source/developer-docs/specification/package.rst

@@ -0,0 +1,33 @@
+.. _package:
+
+==============
+Package Bundle
+==============
+
+All assets get bundled into a custom filetype with an extension of ``.s9pk``, short for Start9 Package. This is the file that will be downloaded from a marketplace. When the user clicks a service's "Install" button, EmbassyOS unpacks and installs the service.
+
+The minimum necessary files for this bundle are:
+
+- image.tar (the result of a Dockerfile build)
+- instructions.md
+- LICENSE
+- icon.png
+
+Each new version release of a service should include the updated version of these files re-bundled into a new ``.s9pk``. . 
+
+Building
+--------
+
+To package all components into an ``.s9pk``, run the following command from the root of your project directory:
+
+.. code:: bash
+
+    embassy-sdk pack
+
+Let's also make sure to verify the validity of the package:
+
+.. code:: bash
+
+    embassy-sdk verify s9pk /path/to/hello-world.s9pk
+
+If anything goes wrong, an error message will indicate the missing component or other failure.