This works well for me and doesn’t require a plugin:

:%norm I<p>^OA</p>

Where the % sign indicates the whole page. Capital I inserts at the beginning of the line

Where ^O represents ctrl-o which exits insert mode. The capital A appends insertion at the end of the line.

Another example covering a range of lines:

:5,25norm I<p>^OA</p>

Is identical except the % sign is replaced by the range of lines you wish to tag.