Add newsletters and memberships features

[supun-io]

Once, Hyvor Talk newsletters and membership features are released:

@Nadil-K

• [ ] Newsletter
  • [ ] Shortcode to embed the newsletter on pages
• [ ] Memberships
  • [ ] Enable/disable memberships
  • [ ] Shortcode to add gated content

@IshiniAvindya

• [ ] new banner with new logo and memberships and newsletters mentioned