Create content for Membership and Benefits

Current preview: https://eclipsefdn-asciidoc-wg.netlify.app/membership/

The current content is implemented as two short-codes. The content of the short-codes is HTML. Instead of two short codes (that are only used in this location) the content could be written as simple AsciiDoc.

Current page: https://github.com/EclipseFdn/asciidoc.eclipse.org/blob/main/content/membership/_index.adoc

Short codes: https://github.com/EclipseFdn/asciidoc.eclipse.org/tree/main/layouts/shortcodes/membership