Add examples for using duckduckgo api for web search

[newdoria88]

Describe the solution you'd like
Currently there's only one example for enabling web search and it relies on using serpapi which is a paid option. I think there should be a free and, if possible, open source option for web search to stay true to the open source nature of the project.

Describe alternatives you've considered
There is already a python package for using duckduckgo but it could also be implemented with an in-house solution, although that would requiere additional work and maintenance but it'd bring the added benefit of less dependence on external code.