feature request: add a markdown summary

Generate a summary markdown file that can be included in build results instead of the entire result document.

As a workaround, this can be done w/ some utilities, but would be nice to have as a built in feature.

```bash
pandoc build/reports/dependency-check-jenkins.html -f html -t gfm | \
sed -n '/## Summary/,/## Dependencies/p' | \
grep -v '## Dependencies' >> $GITHUB_STEP_SUMMARY
```