Flow doc site: error tracking integration

[kerrywei]

Issue To Be Solved

We lack of the capability of error reporting, leaving us in a state where we rely on users to report such errors. To be able to proactively identify & address problems, it's recommended to leverage a modern error tracking system

(Optional): Suggest A Solution

Sentry could be a good fit for this purpose; open to using any other tools that are easy to integrate & can achieve the goal