README: mark external links, add disclaimer...

... and also link it under description.

README.md

@@ -9,13 +9,17 @@ extract-artwork
 
 Takes a number of media files and extracts artwork images.
 
+*Use at your own risk*, pay attention to
+[license and warranty](#license-and-warranty), and
+[disclaimer on external links](#disclaimer-on-external-links)!
+
 Requirements
 ------------
 
 To compile and run `extract-artwork` you need:
 
-* [libav](https://libav.org/) or [ffmpeg](https://www.ffmpeg.org/)
-* [markdown](https://daringfireball.net/projects/markdown/) (HTML documentation)
+* [libav ↗️](https://libav.org/) or [ffmpeg ↗️](https://www.ffmpeg.org/)
+* [markdown ↗️](https://daringfireball.net/projects/markdown/) (HTML documentation)
 
 Some systems may require additional development packages for the libraries.
 
@@ -51,6 +55,21 @@ but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 [GNU General Public License](COPYING.md) for more details.
 
+Disclaimer on external links
+----------------------------
+
+Our website contains links to the websites of third parties ("external
+links"). As the content of these websites is not under our control, we
+cannot assume any liability for such external content. In all cases, the
+provider of information of the linked websites is liable for the content
+and accuracy of the information provided. At the point in time when the
+links were placed, no infringements of the law were recognisable to us.
+As soon as an infringement of the law becomes known to us, we will
+immediately remove the link in question.
+
+> 💡️ **Hint**: All external links are marked with an arrow pointing
+> diagonally in an up-right (or north-east) direction (↗️).
+
 ### Upstream
 
 URL: