fix: `captionRegex` matching error

[Jiasm]

captionRegex matching error occurred when multiple code tags were present.

When some of this text appears in the markdown file:

contentText will be:

'<p><code>code</code>highlight</p>'+
'<pre><code class="javascript">'+
'let text = &#39;something code&#39;'+
'</code></pre>'+
'<p>something <code>wrong</code></p>'

And then, we get a wrong result:

[ele828]

Thanks for you contribution, this change has been included in version 2.2.0

[Jiasm]

You are welcome :)