Add sample for write

[arwinlashawn]

Was using this README to do Cosmos DB data migration with Azure Databricks and realized the sample code for write was missing. I think adding this would greatly help anyone learning to use Databricks for Cosmos DB data migration!

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[kushagraThapar]

LGTM, thanks @arwinlashawn for the contributions.
@FabianMeiswinkel can you please take a look as well?

[arwinlashawn]

Thanks for the prompt review @kushagraThapar ! @FabianMeiswinkel Please let me know if any changes are needed.

[arwinlashawn]

Hi @kushagraThapar , could you please take a look at this PR? Thanks!

[kushagraThapar]

@xinlian12 / @FabianMeiswinkel - please take a look at this.

[arwinlashawn]

Hi @xinlian12, could you please have a look at this PR? Thanks!

[FabianMeiswinkel]

LGTM