[docs] Add new Python SchemaTransform multi-lang guide

[ahmedabu98]

Part of #33358

Adding a new page to the Beam site

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R: @rszper for label website.

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[github-actions]

Reminder, please take a look at this pr: @rszper

[github-actions]

Assigning new set of reviewers because Pr has gone too long without review. If you would like to opt out of this review, comment assign to next reviewer:

R: @liferoad for label website.

Available commands:

• stop reviewer notifications - opt out of the automated review tooling
• remind me after tests pass - tag the comment author after tests pass
• waiting on author - shift the attention set back to the author (any comment or push by the author will return the attention set to the reviewers)