Add algolia search in docusaurus documentation

[DenhamPreen]

User story: As a dev I'd like to search the documentation related to what I'm doing, for example if I find one of my types is RescriptRelay.any I'd like to be able to search it in the documentation and say its would take me to this doc .

Docusaurus docs

Initial discussion here

[zth]

This is now implemented and deployed to prod. Please try it out and see if we can tweak it to be better.