The spec update changes these things:
* It simplifies the HTML regex so that `<!-- a -- b -->` is an HTML
comment. HTML5 reports this as an error, but still parses it.
* It changes the set of known HTML block elements to match HTML5, adding
`search` and removing `source`.
* It adds Unicode Symbols to the set of punctuation characters that are
used to evaluate flankingness.
This commit also changes the declaration HTML regex to match lowercase,
even though that change was technically made in spec version 0.30.
Spec is not clear on how to handle this. Three variations exist:
```
$ echo '' | /home/user/commonmark.js/bin/commonmark
<p><img src="image.png" alt="text <textarea> text" /></p>
$ echo '' | /home/user/cmark/build/src/cmark
<p><img src="image.png" alt="text <textarea> text" /></p>
$ echo '' | /home/user/.local/bin/commonmark
<p><img src="image.png" alt="text text" /></p>
```
Prior to this commit:
- when HTML tags are enabled, tags were removed (as in Haskell version)
- when HTML tags are disabled, tags were escaped (as in C version)
After this commit:
- tags will be escaped (as in C version) regardless of HTML flag
+ render hardbreaks as newlines, same as cmark
Bohan Wei