Remove all attributes from an html tag
<p>i have this html code:</p>

<pre><code>&lt;p style="padding:0px;"&gt;
&lt;strong style="padding:0;margin:0;"&gt;hello&lt;/strong&gt;
&lt;/p&gt;
</code></pre>

<p>but it should become (for all possible html tags):</p>

<pre><code>&lt;p&gt;
&lt;strong&gt;hello&lt;/strong&gt;
&lt;/p&gt;
</code></pre>
