Improve the issue auto-labeling

[hsluoyz]

Sometimes, the issue lavels given by casbin-oa is wrong. We have to fix it manually. We should improve our algorithm and keywords to make it more accurate gradually.

We can first write some Go code inside this repo in the form of Go test or even putting it into the web UI to list all issues that the label has been changed manually, then we improve our algorithm and re-run the algorithm. Then we have three columns:

• A: the original issue label given by the OA
• B: Label given manually by the maintainer
• C: the new label given by the new algorithm

If we can finally get: A != B == C, then our fix is working. Finally we should minimize the count of B != C

[casbin-bot]

@MRGUOKING @kininaru