fix search indexing

[Niennienzz]

• It turns out that Algolia crawler is blocked due to rediection.
• https://dragonflydb.io -> https://www.dragonflydb.io
• I cannot change the configuration myself, contacted Algolia support.
• Will resolve this issue once it's been taken care of.

[Niennienzz]

Thanks to @worldsoup's email, it was very effective, and Algolia changed config on their end to allow the www domain.

I then modified our config, and ran a new crawling session. Now the indexes are up-to-date.

Will keep an eye on this for a while.

[Niennienzz]

Also updated a section in README for myself and any current/future maintainers. 😃