chore(action): support checking issue number prefixed with '#' in github actions for PRs

[empiredan]

Currently PR can pass the check whether an issue is referenced in its description only if the complete URL of the issue can be found, that is, https://github.com/apache/incubator-pegasus/issues/<issue-number>. However, #<issue-number> is also a valid format for github that can be used to generate a URL for the issue, which should also be supported.