[Docs] Add User Guide section: "Data Connectors"

[cosmicBboy]

Description

This User Guide section should highlight the pattern for accessing data outside of Flyte:

• Connecting to a database with one of the SQL-like plugins
  • example of how to read data
  • example of how to write data to a DB
• Specifying and accessing secrets from the tasks
• Connecting to a non-Flyte blob store bucket (similarly, specifying secrets to access it)
  • example of how to read data
  • example of how to write data to blob store
• Connecting to an unsupported database via plugins (e.g. MongoDB or something)
  • example of how to read data
  • example of how to write data

Are you sure this issue hasn't been raised already?

• Yes

Have you read the Code of Conduct?

• Yes

[neverett]

Added to planned work for docs team.