Welcome Gui Cao as new committer

Gui Cao began the code contributions since May 3, 2020. In the past 6 months, his 23 pull requests(GitHub, zifeihan[1]) have been accepted, which includes 5k+ lines of codes.

Meanwhile, he took part in the tech discussion, and show the interests to contribute more to the project.

At Dec. 4th, 2020, the project management committee(PMC) passed the proposal of promoting him as a new committer. He has accepted the invitation at the same day.

Welcome Gui Cao join the committer team.

[1] https://github.com/apache/skywalking/commits?author=zifeihan