Tables should not require three dashes per cell in delimiter row

[jchv]

It looks like GitHub now supports tables with less than three dashes in the delimiter row. Reading in the GitHub Flavored Markdown spec, I don't see anything claiming you need three dashes to make a table, either. Finally, the github/cmark library definitely supports tables with single dash delimiters, a la:

| a | b |
| - | - |
| 1 | 2 |

a	b
1	2

Is it possible this should be revisited now? It's awkward that many other Markdown libraries (including Marked.js and github/cmark) support the syntax with only one dash but Hoedown does not.

Redcarpet also now renders tables with single dashes.

$ apt install ruby ruby-dev
$ gem install --user redcarpet
$ ruby -e "require 'redcarpet'" \
  -e 'markdown = Redcarpet::Markdown.new(Redcarpet::Render::HTML.new(render_options = {}), extensions = {tables: true})' \
  -e 'puts markdown.render("| a | b |\n| - | - |\n| 1 | 2 |")'
<table><thead>
<tr>
<th>a</th>
<th>b</th>
</tr>
</thead><tbody>
<tr>
<td>1</td>
<td>2</td>
</tr>
</tbody></table>

Interestingly, Showdown appears to support tables with two dashes, but not one.

In any case, it appears that this behavior of Hoedown's does not match the popular behavior of GitHub Flavored Markdown as seen on GitHub, GitLab, Jekyll, etc.