1. DDGS().text() - add new parameter backend:
   api - collect data from duckduckgo.com,
   html - collect data from html.duckduckgo.com,
   lite - collect data lite.duckduckgo.com.
2. DDGS().text(backend='api') and DDGS().images() - add sleep(0.75) after receiving the vqd.
3. CLI - ddgs text - add -b (--backend) parameter.
4. add tests for DDGS().text(backend='html') and DDGS().text(backend='lite').