[Docs] Add gate node example for dynamic workflows

[cosmicBboy]

Description

After #3354 is fixed in the UI, add a section in the gate_nodes.py example (see flyteorg/flytesnacks#968) for using gate nodes in a dynamic workflow.

Are you sure this issue hasn't been raised already?

• Yes

Have you read the Code of Conduct?

• Yes

[neelshah2409]

Hey @samhita-alla I would like to work on it .

[TechWizard9999]

😊 "I'd be delighted to work on this issue, @samhita-alla ! Could you please assign it to me?"

[Vishalk91-4]

@samhita-alla, can you please assign this issue to me

[samhita-alla]

Please go ahead and create a PR, @neelshah2409, @TechWizard9999, @Vishalk91-4. We will prioritize PRs based on a first-come, first-serve approach.

[itssiddhantjain]

Hello @samhita-alla, please assign this issue to me as I have already worked on this kind of problem in past and has a great experience.

[neverett]

Added to planned work for docs team, but if someone else opens a PR before we get to it, I'm happy to review.

[dec0dedd]

Hey, I'd like to work on this issue.

[davidmirror-ops]

@dec0dedd Note that we merged a major change to the docs structure yesterday, so please ensure your fork is in sync with the main branch as many sections moved to different location. Thank you!