[ENG] Blog template: Replace Disqus comments integration with feedback CTA to the community forum

Goal

Remove the Disqus comment section from the blog and replace it with a new feedback CTA.

Current Disqus comment section

• The new CTA Figma Link
• Web app link for regular posts
• Web app link for release posts
• Web app link for specific old post pattern

What was changed

• Added the new CTA for, release post template, regular posts template and a old and no so much used post template
• Added the post's title as a parameter to the form URL
• Removed the Disqus from the template.html.haml which was used only for this page

Screenshot example for the link

This MR is also related to -> gitlab-com/marketing/digital-experience/buyer-experience#2311 (closed)

Closes gitlab-com/marketing/digital-experience/buyer-experience#2288 (closed)