Add doc for `index_transform` (#7505)
Add doc for `index_transform` (#7505)

* Add doc for `index_transform`

* update

* Apply suggestions from code review

Co-authored-by: Christine Chen <021c7f81bc4c0e55dbc6c4b2db8d0ea775f269a0@users.noreply.github.com>
Co-authored-by: Florimond Manca <c491f569130f6f25f76edbdf24dcdb8e627dfb7b@gmail.com>

* Change wording

* Apply suggestions from code review

Co-authored-by: Kari Halsted <6202b6c53ae98332d7db2799767b72058d728a62@users.noreply.github.com>

Co-authored-by: Christine Chen <021c7f81bc4c0e55dbc6c4b2db8d0ea775f269a0@users.noreply.github.com>
Co-authored-by: Florimond Manca <c491f569130f6f25f76edbdf24dcdb8e627dfb7b@gmail.com>
Co-authored-by: Kari Halsted <6202b6c53ae98332d7db2799767b72058d728a62@users.noreply.github.com>
DataDog/integrations-core,DataDog/integrations-core,DataDog/integrations-core,DataDog/integrations-core,DataDog/integrations-core,DataDog/integrations-core,DataDog/integrations-core,DataDog/integrations-core,DataDog/integrations-core,DataDog/integrations-core