Update the documentation to reflect typescript changes from v 4.5.1

Prerequisites

[X] I have written a descriptive issue title
[X] I have searched existing issues to ensure the issue has not already been raised

Issue

Documentation on typescript changes in v. .4.5.1 should be made. It should be made clear that mixing callback and async-await style is not permitted, to avoid reports like #220 . Also it should be detemined if the "TypeScript Contextual Inference" as described in the Readme.md is still an issue and corrected if necessary.

fastify / fastify-plugin

Update the documentation to reflect typescript changes from v 4.5.1 #221

Prerequisites

Issue