docs(samples): add samples for events

[tetiana-karasova]

Thank you for opening a Pull Request! Before submitting your PR, there are a few things you can do to make sure it goes smoothly:

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Fixes #<issue_number_goes_here> 🦕

[snippet-bot]

Here is the summary of changes.

You are about to add 3 region tags.

• samples/interactive-tutorials/events/import_user_events_big_query.py:22, tag retail_import_user_events_from_big_query
• samples/interactive-tutorials/events/import_user_events_gcs.py:20, tag retail_import_user_events_from_gcs
• samples/interactive-tutorials/events/import_user_events_inline.py:16, tag retail_import_user_events_from_inline_source

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