✨ Added Giscus discussions and reactions

[babakamyljanovssw]

Relates to #1567

• Added Giscus package
• Added Giscus discussion on top of Disqus comments
  As per this comment ✨ Added giscus integration #1382 (comment) from old PR that adds Giscus, Adam suggested we have Giscus and Disqus for now.
• Removed custom <Reactions /> component and it's css
• Mapped discussion with rule using GUID, and I was able add reaction to rule locally (please see screenshot below)
• Added GitHub secrets

Also, to link existing discussions from the Chewing the Fat, we can add computed sha1 of rule GUID to the discussion body in below format.
<!-- sha1: dcbb7fedfd3bd7f69fe677a3d5e60a6f211646ba -->

Figure: Giscus is added on top of Disqus

[JackDevAU]

As per this comment #1382 (comment) from old PR that adds Giscus, Adam suggested we have Giscus and Disqus for now.

Not sure this is amazing.... but I understand we don't want to lose the information... Can we hide Disqus it for now and slowly add it back later?

[JackDevAU]

✅