[PROPOSAL] Release of 2.1.1

[Tian Jiang]

Greetings,


It has been about a month since we released Apache TsFile 2.1.0 and there are 
some fixes and improvements since then.
Some of them are desired by communities like Apache IoTDB, so I propose to 
release the version 2.1.1.


Best,
Tian Jiang