Add documentation on how to make sure Gravity Foms complies with GDPR

[rianrietveld]

If the form asks for personal data, this data can be stored in the database. Here GDPR legistation applies.
The users must be aware of this and also know how to act.

Two good resources:

• The documentation of Gravity Forms: WordPress, Gravity Forms, and GDPR Compliance
• Post by CosmicGiant from 2022 with helpful info: Complete Guide to Gravity Forms GDPR Compliance in WordPress