Support for viewing sent links in Whatsapp messages

[Robi9]

Support to include a URL preview in messages with links sent on Whatsapp. Add "preview_url": true to the message body as indicated in the documentation.

[codecov]

Codecov Report

Merging #431 (c15c3d6) into main (2d19d67) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #431      +/-   ##
==========================================
+ Coverage   71.90%   71.93%   +0.02%     
==========================================
  Files          95       95              
  Lines        8387     8394       +7     
==========================================
+ Hits         6031     6038       +7     
  Misses       1757     1757              
  Partials      599      599              

Impacted Files	Coverage Δ
handlers/whatsapp/whatsapp.go	77.28% <100.00%> (+0.32%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 2d19d67...c15c3d6. Read the comment docs.