feature request: add "accepts json requests" field

[ilyapashuk]

hello

as I know, many of public searx instances, but not all, forbids usage of the request api.

on request like this:
host/search?q=something+site:dzen.ru&format=json

they returns 403 error.

please add an other field to the public instances list to contain information weather instance allows the json requests.

[unixfox]

@dalf should we provide this kind of information?

I feel like searx(ng) hasn't been designed to be used by external programs in mind so I'm not sure here if we should add this info.

If we add this kind of information this may increase the amount of bots on the public instances, something that we have been fighting against it. But I guess if an instance has JSON/CSV/xml output enabled it's that they don't care about bots.

@searxng/internal maybe you could give your feedback on this?