We now have a few places where the long description (ldesc) for a
package is used (in the package summary webpage, in the tooltip for the
package description in setup, and now in any automatically generated
announce email).
Unfortunately, it's underspecified exactly what a newline in ldesc
means, and taking it literally causes problems when trying to render it
nicely in those places. (Some heuristic hacks are already applied to it
in the package summary webpage to try to make things look reasonable)
Therefore, I'm proposing to define that the following very minimal
subset of MarkDown-compatible markup can be used in ldesc:
* A blank line separates paragraphs
* A line ending with two (or more spaces) is followed by a line break
* Lines starting with '-', '*', or '+' are bulleted lists
- Sublists are indented by four spaces
(Technically, all of this also applies to the message: hint, being the
only other hint which can take a multi-line value, but since that's only
used by one package currently, that's not much of a concern)