Adding Elestio as one-click deployment option

Hey team,
I am Kaiwalya, Developer Advocate at Elestio. Elestio has been providing options of fully deploying and managing Hasura application [as shown here](https://elest.io/open-source/hasura). I think it would be a great idea if we can add it to official readme/documentation here.
In addition to this, if you are interested we provide collaboration opportunities with tools we support by revenue share upon addition of this method in docs. If you would like to collaborate, just drop me an email at [kaiwalya@elest.io](mailto:kaiwalya@elest.io) :)

The issue points to the official README/documentation and provides the Elestio deployment page; start by locating the existing deployment-options section and reviewing its format. Done means adding a clear Elestio one-click deployment entry with the supplied link and confirming the documentation renders correctly.

Written by the indexing model from the issue text.