Add search suggestions

[krojew]

Search providers support real-time search suggestions, which can save a lot of time (e.g. https://suggestqueries.google.com/complete/search?output=toolbar&hl=en&q=test). It would be great to have such functionality in Heimdall.

[KodeStar]

Added in #1523 it currently has support for bing, duckduckgo and google. Will be in the next release whenever that is, feel free to test the code though, the development tag will have the changes.