RFE: add new RSS feed only for extensions

[remicollet]

Nothing listed in https://packagist.org/feeds/

I know https://packagist.org/feeds/vendor.pecl.atom may help

Perhaps something like

• https://packagist.org/feeds/extensions.packages.atom (new packages)
• https://packagist.org/feeds/extensions.releases.atom (new releases)