feat: describe new customOptions fields in the DLE configration reference (database-lab#361)

Description

Describe new customOptions fields in the DLE configration reference

Related issue

database-lab#361 (closed)

Examples

Checklist

• the MR description has been reviewed
• this MR contains text changes and they have been reviewed OR there are no texts changes
• this MR contains GUI/CLI changes and they have been reviewed OR there are no GUI/CLI changes
• this MR contains API changes and they have been reviewed OR there are no API changes