[mod] engine yep.com: show all 100 results yep.com has

yep.com is still in beta, the api.yep.com does not have paging support.  There
is only a 'limit' argument with a maximum of 100 results.

yep.com seems fast; there is nor need for a timeout of 12 sec.

The API returns JSON nevertheless what the HTTP header is, the "show more"
button on yep.com's web site does not set a special HTTP Accept header.

FYI: The index does not support languages, the WEB UI does not offer a language
selection of the results and the entire index seems in English.

Closes: https://github.com/searxng/searxng/issues/1619


Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>