[Task]: Validate playground snippets in website documentation

[Amar3tto]

What needs to happen?

Playground snippet example:

{{< playground height="700px" >}} {{< playground_snippet language="py" path="SDK_PYTHON_FlatMapLambda" show="flatmap_lambda" >}} {{< /playground >}}

We need to check that there is a correct .py file with name: FlatMapLambda and it has [START flatmap_lambda] and [END flatmap_lambda].
This validation is needed for all Python/Java playground snippets.

Issue Priority

Priority: 2 (default / most normal work should be filed as P2)

Issue Components

• Component: Python SDK
• Component: Java SDK
• Component: Go SDK
• Component: Typescript SDK
• Component: IO connector
• Component: Beam YAML
• 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

[Amar3tto]

.take-issue