[Feature][Doc] Improved connectors v2 contribution guide

[Mr-LiuXu]

..was encountered https://github.com/apache/incubator-seatunnel/issues/2541

Purpose of this pull request

Improve the connector-v2 contribution guide and add common basic modules and formats to help new developers enter development more quickly

Check list

• [x] Code changed are covered with tests, or it does not need tests for reason:
• [x] If any new Jar binary package adding in your PR, please add License Notice according New License Guide
• [x] If necessary, please update the documentation to describe the new feature. https://github.com/apache/incubator-seatunnel/tree/dev/docs

[Mr-LiuXu]

I have improved the document, can you take a look.

[Mr-LiuXu]

I have improved the document, can you take a look.