Add Readme and the policy file required

Or running ratbagd (as root) raises a "Permission denied".

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@gmail.com>

README.md

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+ratbagd
+=======
+
+ratbagd is a system daemon to introspect and modify configurable mice.
+
+Running ratbagd
+---------------
+
+To be able to run ratbagd, you need to add a policy file to your dbus
+environment:
+
+    sudo cp dbus/org.freedesktop.ratbag1.conf /etc/dbus-1/system.d/org.freedesktop.ratbag1.conf
+
+License
+-------
+
+libratbag is licensed under the MIT license.
+
+> Permission is hereby granted, free of charge, to any person obtaining a
+> copy of this software and associated documentation files (the "Software"),
+> to deal in the Software without restriction, including without limitation
+> the rights to use, copy, modify, merge, publish, distribute, sublicense,
+> and/or sell copies of the Software, and to permit persons to whom the
+> Software is furnished to do so, subject to the following conditions: [...]

dbus/org.freedesktop.ratbag1.conf

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+<?xml version="1.0"?> <!--*-nxml-*-->
+<!DOCTYPE busconfig PUBLIC
+        "-//freedesktop//DTD D-BUS Bus Configuration 1.0//EN"
+        "http://www.freedesktop.org/standards/dbus/1.0/busconfig.dtd">
+
+<busconfig>
+
+        <policy user="root">
+                <allow own="org.freedesktop.ratbag1"/>
+                <allow send_destination="org.freedesktop.ratbag1"/>
+                <allow receive_sender="org.freedesktop.ratbag1"/>
+        </policy>
+
+</busconfig>