This patch is a a complete revision of the article "Offline engines", which also
merges the content from the searx-wiki [1] into this article.
[1] https://github.com/searx/searx/wiki/Offline-engines
Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>
The article "Offline engines" should be in developer's documentation next to
chapter "Engine overview".
Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>
