Header slugger does not properly handle embedded HTML

[Gerrit0]

Search terms

slugger, anchor links

Expected Behavior

TypeDoc's anchor generation output should match output generated by other common markdown renderers.

(with html in markdown turned off)
# foo <T>
(with html in markdown turned on)
# bar &lt;T&gt;

The above headers should have the slug foo-T and bar-T (if the slugger's lowercase option is off)

Actual Behavior

Today TypeDoc generates foo- and bar- due to stripping the HTML

Environment

• TypeDoc version: 0.28.12