More incremental improvements to community contributions

In February 2022, we launched a new feature called community contributions to security advisories. We've continued to iterate on this feature, and recently released more improvements:

• You're now prompted to add a reason for the change, so your contribution can be reviewed more quickly.
• You can now submit a contributions without reference links getting reordered in the diff.
• You can now click through to relevant docs from the advisories page.
• You can overall enjoy a cleaner UX experience through a handful of other small fixes.

Further reading:

• Learn more about the GitHub Advisory Database
• Learn more about GitHub community contributions