add VTEX Ads API

[julia-rabello]

partially adding VTEX Ads API reference with the following endpoints:

Catalog synchronization
POST Synchronize product information
POST Synchronize inventory information

Ads events notification
POST Track ad impressions
POST Track ad clicks
POST Track ad views
POST Track conversions

Ads
POST Get ads

Types of changes

• New content (endpoints, descriptions or fields from scratch)
• Improvement (make an endpoint's title or description even better)
• Spelling and grammar accuracy (self-explanatory)

Changelog

Do not forget to update your changes to our Developer Portal's changelog. Did you create a release note?

• Yes, I already created a release note about this change.
• No, but I am going to.

[github-actions]

Thanks for your contribution. The .json file will be checked now with Spectral.