[KYUUBI #2516] [DOCS] Add Contributor over time in README.md

### _Why are the changes needed?_

Add Contributor over time in README.md

### _How was this patch tested?_
- [ ] Add some test cases that check the changes thoroughly including negative and positive cases if possible

- [x] Add screenshots for manual tests if appropriate

- [ ] [Run test](https://kyuubi.apache.org/docs/latest/develop_tools/testing.html#running-tests) locally before make a pull request

![image](https://user-images.githubusercontent.com/70557521/165920534-3834564b-071e-4158-9056-d9460b0554a7.png)

Closes #2516 from yangrong688/patch-2.

Closes #2516

53a2f35 [yangrong688] Add Contributor over time in README.md

Authored-by: yangrong688 <70557521+yangrong688@users.noreply.github.com>
Signed-off-by: Kent Yao <yao@apache.org>

Author: yangrong688

README.md

@@ -107,6 +107,10 @@ Ready? [Getting Started](https://kyuubi.apache.org/docs/latest/quick_start/quick
 
 ## [Contributing](./CONTRIBUTING.md)
 
+## Contributor over time
+
+[![Contributor over time](https://contributor-graph-api.apiseven.com/contributors-svg?chart=contributorOverTime&repo=apache/incubator-kyuubi)](https://api7.ai/contributor-graph?chart=contributorOverTime&repo=apache/incubator-kyuubi)
+
 ## Aside
 
 The project took its name from a character of a popular Japanese manga - `Naruto`.