[ruby/rdoc] Allow rich definition list labels for Markdown

Previously, any sort of "rich" markup for a definition list's label
would cause the Markdown parser to not recognize a definition list:

```ruby
md = <<~md
`one`
:    This is a definition
md

doc = RDoc::Markdown.parse(md)
doc # => [doc: [para: "<code>one</code>\n: This is a definition"]]
```

This commit tweaks the grammar for Markdown definition lists so that
labels can include "rich" markup such as bold (`**`), code (```), etc:

```ruby
md = <<~md
`one`
:    This is a definition
md

doc = RDoc::Markdown.parse(md)
doc # => [doc: [list: NOTE [item: ["<code>one</code>"]; [para: "This is a definition"]]]]
```

The [PHP Markdown Extra][1] Spec does not seem to specify whether or not
this should be allowed, but it is allowed in the RDoc format:

```ruby
rdoc = <<~rdoc
+code+::
    This is a definition
rdoc

doc = RDoc::Markup.parse(rdoc)
doc # => [doc: [list: NOTE [item: ["+code+"]; [para: "This is a definition"]]]]
```

so accepting this change increases the parity of the two formats.

[1]: https://michelf.ca/projects/php-markdown/extra/#def-list

https://github.com/ruby/rdoc/commit/8f943bbba4

0 files changed, 0 insertions, 0 deletions