[reflow] more elements per shelf

[mchangrh]

On channel pages, elements are left-aligned and don't reflow accordingly

• hook into right arrow click to populate new elements
• reflow elements according to width

[ajayyy]

Removing ytd-rich-item-renderer and ytd-video-meta-block[rich-meta] #metadata-line.ytd-video-meta-block from the style seems to have a better effect. No empty slots

[mchangrh]

probably died with reflow https://github.com/mchangrh/yt-neuter/commit/e45e79ae4fe7448941808c29b5434e104f9b599b