* Make any frontmatter <scheme>:// URI's clickable http/https links are opened in a new tab/window (via target="_blank"), other schemes are opened in the current tab, as the browser will prompt the user to open another application (or do this automatically). Per https://www.rfc-editor.org/rfc/rfc3986#section-3.1, the scheme must follow the pattern: scheme = ALPHA *( ALPHA / DIGIT / "+" / "-" / "." ) * Make `mailto:...` strings clickable in frontmatter