[Task]: Show a loading indicator while switching examples

[alexeyinkin]

What needs to happen?

Currently we only show the loading indicator when an example is first loading.

This indicator is also important for tests because they can wait for the animation to finish before checking if the example is changed.

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

[alexeyinkin]

.take-issue