Improve/trim the user manual further

Detailed information can be found on Wikipedia. The user manual
should be a compact documentation of the mod as whole.
This replaces long explanations with relevant links for use by
people who are interested in going deeper into this matter.

LICENSE.txt

@@ -0,0 +1,16 @@
+Minetest Mod: technic
+Copyright (C) 2012-2022  RealBadAngel and contributors
+
+This library is free software; you can redistribute it and/or
+modify it under the terms of the GNU Lesser General Public
+License as published by the Free Software Foundation; either
+version 2.1 of the License, or (at your option) any later version.
+
+This library is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public
+License along with this library; if not, write to the Free Software
+Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA

README.md

@@ -25,6 +25,7 @@ world. A few notable features:
 ## FAQ
 
 The modpack is explained in the **[Manual](manual.md)** included in this repository.
+Machine and tool descriptions can be found on the **[GitHub Wiki](https://github.com/minetest-mods/technic/wiki)**.
 
 1. My technic circuit doesn't work. No power is distributed.
     * Make sure you have a switching station connected.
@@ -38,7 +39,7 @@ For modders: **[Technic Lua API](technic/doc/api.md)**
 ## License
 
 Unless otherwise stated, all components of this modpack are licensed under the
-LGPLv2 or later. See also the individual mod folders for their
+[LGPLv2 or later](LICENSE.txt). See also the individual mod folders for their
 secondary/alternate licenses, if any.