Allow non-functional package changes without bumping version number

Occasionally, I screw up package releases with typos or mis-linked images in informational files such as the `README` or `LICENSE` or `CHANGELOG` or other docs.

When I make those mistakes, I'd like to fix them without needing to bump my package version, and also delist the previous version.

I'd like for my package version to reflect the evolution of behaviors within that package, not the evolution of non-functional supplemental artifacts. In other words, I'd like to be able to change a README without changing my package version.

Similarly, there's a new feature on Pub that pulls some information from the pubspec. I'd like to be able to alter that information as well, without bumping the package version.

Start by mapping how pub.dev handles package versions, releases, informational files, and pubspec-derived metadata. Define which non-functional changes may be published without a version bump and how the previous version should be delisted; the issue names no files or tests, so the relevant entry points and completion checks must first be established.

Written by the indexing model from the issue text.