Markdown: links in HTML blocks, block transclusions and e"..." values

Three problems with WikiText inside text/markdown tiddlers. Paste each example into a new tiddler of type text/markdown. The markdown plugin is unchanged since v5.4.0; tested on master 8c599e64c.

1. [[links]], [img[...]] and [ext[...]] stay literal inside an HTML block, while macros and transclusions in the same block work:

[[HelloThere]] is a link outside an HTML block.

<div>
[[HelloThere]] and [ext[https://tiddlywiki.com]] stay text inside one, but <<version>> works.
</div>

The readme says HTML blocks are parsed by the WikiText parser, but wrapper.js removes these three rules from that parser because markdown-it handles them, and markdown-it does not look inside HTML blocks.

1. A transclusion in its own paragraph renders inline, so the first list shows as * one * two. Only the second, with $mode="block", is a list:

<$let items="""* one
* two""">

<$transclude $variable="items"/>

<$transclude $variable="items" $mode="block"/>

</$let>

The final WikiText pass uses parseAsInline: true.

1. An e"..." attribute value only works in an HTML block. Inside a paragraph the whole widget is shown as text:

<$text text=e"&#9733; works in its own block"/>

A paragraph: <$text text=e"&#9733; fails"/>

A paragraph with a plain value: <$text text="★ works"/>