[Task]: Update document for spark runner

[HaoXuAI]

What needs to happen?

The Spark runner document doesn't explain how to run a beam job on a Spark Kubernetes cluster. At Affirm, we are able to do that by submitting the beam job to the spark cluster without the need for an extra job server.
Action item:

• Update the document to include how to submit the beam job to Spark Cluster.

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

[HaoXuAI]

.take-issue
PR: #27984