Show package security advisories and/or "report a security issue" button on packages

[chreekat]

Related to haskell/security-advisories#7

cc @frasertweedale -- I looked briefly but couldn't find any coordinating issue somewhere else

[frasertweedale]

@chreekat thank you for filing this. I think this is the best place to track it but if there is any specific needs that you want SRT to help with, please create issues in the security-advisories repo for those.