### _Why are the changes needed?_
Add generate_changelog.sh script to simple generate changelog for Apache Incubating Kyuubi.
I've searched there are generaly three ways to generate changelog
1. add change log manually in ervery pr ([Apache Skywalking](https://github.com/apache/skywalking/pull/8881/files#diff-e4d10d406c447edb82b7e7958bebc5ff8ca9123076cf138b4e0ba037fa873055))
2. use github action to generate ([sqlfluff](https://github.com/sqlfluff/sqlfluff/blob/main/.github/release-drafter.yml))
3. use script to generate changelog
I choose to write a script to generate changelog, it does not rely on github and we can use it more conviniently as there maybe mutiple release candidates in the release process.
I add a script to generate changelog once we prepare a new release version, it allows release manager to easy generate changelog between last release tag and current release tag.
And the changelog doc structure is:
$KYUUBI_DIR
    /docs
        /changelog
            /v1.5.1-incubating.md
            ...
### _How was this patch tested?_
use `./generate_changelog.sh v1.5.0-incubating v1.5.1-incubating-rc0` to generate v1.5.1-incubating changelog
Closes#2501 from yangrong688/KYUUBI-2211.
Closes#2211
b3174b4d [yangrong688] Add generate_changelog.sh script to simple generate changelog for Apache Incubating Kyuubi.
Authored-by: yangrong688 <yangrong.jxufe@gmail.com>
Signed-off-by: ulysses-you <ulyssesyou@apache.org>
dd96983be9