[ANNOUNCE] Paimon Improvement Proposal (PIP)

[Jingsong Li]

Hi devs,

Paimon Improvement Proposal (PIP) has been created at the confluence.
Most of the content is copied from Apache Flink.

[1] 
https://cwiki.apache.org/confluence/display/PAIMON/Paimon+Improvement+Proposals

Best,
Jingsong