[Docs] Add example notebook for enrichment transform with bigtable (a…

…pache#30315)

* bigtable enrichment notebook

* Update examples/notebooks/beam-ml/bigtable_enrichment_transform.ipynb

Co-authored-by: Rebecca Szper <[email protected]>

* Update examples/notebooks/beam-ml/bigtable_enrichment_transform.ipynb

Co-authored-by: Rebecca Szper <[email protected]>

* Update examples/notebooks/beam-ml/bigtable_enrichment_transform.ipynb

Co-authored-by: Rebecca Szper <[email protected]>

* Update examples/notebooks/beam-ml/bigtable_enrichment_transform.ipynb

Co-authored-by: Rebecca Szper <[email protected]>

* Update examples/notebooks/beam-ml/bigtable_enrichment_transform.ipynb

Co-authored-by: Rebecca Szper <[email protected]>

* Update examples/notebooks/beam-ml/bigtable_enrichment_transform.ipynb

Co-authored-by: Rebecca Szper <[email protected]>

* Update examples/notebooks/beam-ml/bigtable_enrichment_transform.ipynb

Co-authored-by: Rebecca Szper <[email protected]>

* Update examples/notebooks/beam-ml/bigtable_enrichment_transform.ipynb

Co-authored-by: Rebecca Szper <[email protected]>

* Update examples/notebooks/beam-ml/bigtable_enrichment_transform.ipynb

Co-authored-by: Rebecca Szper <[email protected]>

* changes from the review

* Apply suggestions from code review

Co-authored-by: Rebecca Szper <[email protected]>

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Co-authored-by: Rebecca Szper <[email protected]>