If there is whitespace in the element containing the value to be copied
then Firefox[1] includes that space in the value it puts in the clipboard.
This is obviously annoying since `foo-bar` might be a valid API key where
`foo-bar ` is not.
This commit fixes that by using the `-` in Jinja to gobble whitespace.
I also looked at doing this in the Javascript, but the browser API for
selecting some text and copying it doesn’t give an obvious place for
using `String.prototype.trim()`.
1. Tested with Firefox 100.0 on Mac OS 12.2.1
