docs: add epilog.rst to define common things.

docs/introduction.rst

@@ -11,6 +11,28 @@ Why Backup?
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+Features
+--------
+
+:Proxmox VE: The `Proxmox Virtual Environment`_ is fully
+   supported. You can backup :term:`virtual machine`\ s and
+   :term:`container`\ s.
+
+:GUI: We provide a graphical, web based user interface.
+
+:Deduplication: Inkremental backup produces large amounts of duplicate
+   data. The deduplication layer removes that redundancy and makes
+   inkremental backup small and space efficient.
+
+:Remote Sync: It is possible to efficently synchronize data to remote
+   sites. Only deltas containing new data are transfered.
+
+:Performance: The whole software stack is written in :term:`Rust`,
+   which provides high speed and memory efficiency.
+
+:Open Source: No secrets. You have access to the whole source tree.
+
+
 History
 -------