[ADD] website_forum_seo: add new module for improve forum que/ans description


<b>Task:</b> https://www.odoo.com/web#id=9107&view_type=form&model=project.task&menu_id=3942&action=327
<b>Pad:</b> https://pad.odoo.com/p/r.aAXbFLdZvu62soZi


<b>New Module:</b> website_forum_seo
<b>VIew Demo:</b> https://www.youtube.com/watch?v=_lYH_GrRqso

yes is this necessary for,
<b>point 1:</b> Preventing the replace keyword inside URL for example:
   <code>&lt;a href="www.keyword.com"&gt; keyword &lt;/a&gt; </code>

<b>point 2:</b> First time when keyword replace to a new replaced, next time does not replace same word again. for Identifying this we add span tag before and after for example:
   <code>&lt;span&gt; replaced_word &lt;span&gt;</code>

<b>point 3:</b> If statement is like <code>this is new url www.keyword.com </code> we can't replace this www. or .com inside word.