doc: add a file describing the package format

doc/package-format.txt

@@ -0,0 +1,41 @@
++------------------------------------------------------------------------------+
+|                   Rosetta Package Manager Documentation                      |
+|                   .....................................                      |
+|                         Package Format And Layout                            |
++------------------------------------------------------------------------------+
+
+   This document describes the format and layout of Rosetta package files.
+
+
+1 Main Package Layout
+=====================
+
+   The main package is an uncompressed tar archive that contains a set of
+   compressed files and sub-archive.
+
+   The contents of the main package include:
+   -  /data.tar.zst : Contains the files to be extracted to the system
+      directory when the package is installed.
+
+   -  /control.tar.zst : Contains a set of scripts to be executed at different
+      points in the package (un)installation process.
+
+   -  /meta.tar.zst : Contains information about the package itself, including
+      the manifest and news data.
+
+
+2 The Payload Package
+=====================
+
+
+3 The Control Package
+=====================
+
+
+4 The Meta Package
+==================
+
+
+*****!
+
+vim: shiftwidth=3 expandtab