[Feature Request]: Use the canonical link when generating javadoc

[liferoad]

What would you like to happen?

Using google search such as Kafka IO could lead to the old javadoc for Beam. We can use the canonical link when generating the javadoc and always point it to current.

Issue Priority

Priority: 3 (nice-to-have improvement)

Issue Components

• Component: Python SDK
• Component: Java SDK
• Component: Go SDK
• Component: Typescript SDK
• Component: IO connector
• Component: Beam examples
• Component: Beam playground
• Component: Beam katas
• Component: Website
• Component: Spark Runner
• Component: Flink Runner
• Component: Samza Runner
• Component: Twister2 Runner
• Component: Hazelcast Jet Runner
• Component: Google Cloud Dataflow Runner

[liferoad]

I believe we could do this for other SDK docs.