updated settings.yml to new searx 1.0.0 relevant entries...
- switched theme to default oscar with logicodev-dark style. (= priza theme needs updating, though it can still be chosen from preferences.)
- new engines added.
- some existing engines disabled by default for causing too many errors, others enabled.
- csp headers update.

@stinpriza
Congrats, Has searx dark mode?

@panigrc yes, there is a dark mode with oscar theme and logicodev dark style. (from preferences).