### _How was this patch tested?_
- [ ] Add some test cases that check the changes thoroughly including negative and positive cases if possible
- [ ] Add screenshots for manual tests if appropriate
- [ ] [Run test](https://kyuubi.readthedocs.io/en/latest/develop_tools/testing.html#running-tests) locally before make a pull request
Closes#1099 from simon824/doc.
Closes#1099
6830ec21 [simon] add SparkSQL Extension config document
Authored-by: simon <zhangshiming@cvte.com>
Signed-off-by: ulysses-you <ulyssesyou@apache.org>
6898f5d09a