Merge pull request #21 from sundowndev/fix/duckduckgoURL

Fix DuckDuckGo search URL

docs: readme

Merge pull request #8 from sundowndev/feat/string

Use default Go string conversion

Merge pull request #5 from sundowndev/refact/engineFactory

Export engine factory

docs: update readme exemples

docs: godoc

fix: add group method to EngineFactory

chore: readme