HTML entities are not handled correctly

[wwalc]

I just created a broken issue, because I did not wrap an HTML tag with the code tag. Typing as plain text the content below:

Writing some code tags: <h1>, <h2>, <h3>... 

results in...

Writing some code tags:

,

,

...

---

In theory, this is how the default text input in GitHub works. This is however slightly counterintuitive as in WYSIWYG editors whatever is typed by the user in the editing area is treated as "plain text" and converted to entities. Not sure what should be the correct behavior.

[fredck]

This is an issue with the markdown plugin. I've reported it here:
ckeditor/ckeditor5#5997

To note that using HTML entities is wrong. According to the GFM specs, the output markdown should instead escape the HTML tags with slash, like \<h1>.

[fredck]

This issue is now fixed in ckeditor/ckeditor5-markdown-gfm#29.