Lone quote in heading text breaks trailing-attribute detection

[PiotrCzapla]

A lone ' or " in heading text breaks trailing-attribute detection.

Ok (without quotes):

from mdhtml import to_mdhtml
print(to_mdhtml('# Alpha beta {k="v"}'), end="")

<h1 k="v">Alpha beta</h1>

Broken:

print(to_mdhtml("# Alpha's beta {k=\"v\"}"), end="")

<h1>Alpha's beta {k="v"}</h1>

Broken:

print(to_mdhtml("# [Alpha]{.cls} the firm's charter {k=\"v\"}"), end="")

<h1 class="cls}" firm's charter {k="v">[Alpha]</h1>

https://share.solveit.pub/d/9c078ad0441301956d58171fece9c4ac