Avoid clipping of the Runeword popup at bottom of the browser viewport

[fabd]

Avoid clipping the popup, particularly if user has zoom level > 100% in the browser.

Possible implementation:

• make the popup fixed position, always center and top of the viewport -- regardless of page scroll
• (optional) make the header also fixed so it stays on the page (would look nicer I think once the popup is "stuck" to the top edge, makes the top area less empty looking)

[fabd]

make the popup fixed position, always center and top of the viewport -- regardless of page scroll

Looks ugly, so meh.

TODO

• keep the current positioning next to the Runeword name, which feels intuitive, but also calculate the popup height, and move it vertically so it doesn't get clipped at bottom of page