added bulk upsert example

[sureshdsk]

What kind of change does this PR introduce?

Doc update
Added bulk upsert example to docs - #3089

[vercel]

This pull request is being automatically deployed with Vercel (learn more).
To see the status of your deployments, click below or on the icon next to each commit.

docs – ./web

🔍 Inspect: https://vercel.com/supabase/docs/5jHRVZTGKdtYRfE4T8tPquT7PMZB
✅ Preview: https://docs-git-fork-sureshdsk-upsert-doc-supabase.vercel.app

www – ./www

🔍 Inspect: https://vercel.com/supabase/www/AyvkzFv66a2pXEuNnDvoL5ZM4ZLM
✅ Preview: Canceled

[Deployment for 94d345e canceled]

about – ./about

🔍 Inspect: https://vercel.com/supabase/about/DWio2HTAYS3ppWUi7Yg3KKAGawZc
✅ Preview: https://about-git-fork-sureshdsk-upsert-doc-supabase.vercel.app

main – ./

🔍 Inspect: https://vercel.com/supabase/main/2WbYv5qeZLA3UqDLZBaWg1MWoFpq
✅ Preview: https://main-git-fork-sureshdsk-upsert-doc-supabase.vercel.app

[kiwicopple]

really nice addition to the docs @sureshdsk - just one change requested :)