Prerelease blog post improvements

[platinumazure]

A few improvements that might be worth pursuing for prereleases:

• Blog post should look at the release version related to latest stable (rather than just the issue tags), so that all prereleases show as major
• Blog post should include "Installing" info if prerelease (and could embed release version in easily)
• Blog post should include "Migration Guide" info if project is ESLint and release type is prerelease