add document for how contributors can be granted more rights such as commit access or decision power is clearly documented

[luoyuxia]

Search before asking

• I searched in the issues and found nothing similar.

Description

according to https://cwiki.apache.org/confluence/display/FLUSS/Maturity+Assessment+for+Apache+Fluss
CO50 "The way in which contributors can be granted more rights such as commit access or decision power is clearly documented and is the same for all contributors."
Seem we are missing this part to document how contributors can be granted more rights.

https://paimon.apache.org/docs/master/project/committer/
Paimon can be a good reference.

Willingness to contribute

• I'm willing to submit a PR!

[matrixsparse]

Hi @luoyuxia, I'd like to work on this documentation. I'll reference Paimon's committer guide and draft a similar document for Fluss. Could you please assign this issue to me?