Add ISO-GQL to Open-source Edition #6161

https://nebula-graph.io/pricing

1. Open-source Edition: nGQL/openCypher
2. Enterprise Edition: ISO-GQL
3. NebulaGraph Cloud: ISO-GQL

Suggestion: Add ISO-GQL to Open-source Edition

Reasoning: Make the "Open-source Edition" useful for users that

• want to minimize vendor lock-in
• want to use "ISO-GQL" (as the NebulaGraph specific ISO GQL implementation)
• want to use a query language close to ISO GQL