GitHub supports the use of HTML comment blocks in markdown that show up
in the raw text of a Markdown body but are not rendered.

This is perfect for instructional text, as it makes it visible to the authors when
editing the text, but does not take up room in the rendered markdown (where
it does not need to be visible)

[Rendered version (where comments are hidden)](https://github.com/psigen/bazel/blob/patch-3/ISSUE_TEMPLATE.md)

Closes #14227.

PiperOrigin-RevId: 417420651