Add link tag in htmlpair (must be closed)

[raimonesteve]

Link tag ("a") must be closed because change to ">" to html entities.

Example:

text = '<a href="/hello-world">Hello World </a> and  [/thanks-wikimarkup thanks wikimarkup]'

Render:

<p>&lt;a href="/hello-world"&gt;Hello World &lt;/a&gt; and  <a href="/thanks-wikimarkup">thanks wikimarkup</a></p>

With this PR, render will be:

<p><a>Hello World </a> and  <a href="/thanks-wikimarkup">thanks wikimarkup</a></p>