[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

Here words are sore into a Tuple. So when accessing value of tuple using index <code>i.e. like seo_word[0]</code> (means keyword) not clearly know which is the key name(because tuple access index value 0,1 etc..) that's why existing <code>keyword, replacement_word, url, case_sensitive</code> good for this case.