Add Sticky Notes syntax guide and a new community contribution

[huyphung1602]

Summary

Add the following things:

• Sticky Notes syntax guide
• A new community contribution

Issue

(issue link here)

Lasting Changes (Technical)

• Sticky Notes syntax guide.
• A new community contribution (SchemaToDbml from Ricardo Ribeiro).

Checklist

Please check directly on the box once each of these are done

• [ ] Documentation (if necessary)
• [ ] Tests (integration test/unit test)
• [ ] Integration Tests Passed
• [x] Code Review

[TeaNguyen]

Since the "Note Definition" already mentions that "Note allows users to give description for a particular DBML element." Perhaps we can bring the Sticky Notes outside, between the "Comments" and "Note Definition" to avoid users misunderstanding that the sticky notes will be defined under any element's scope