Intent to ship: CSS `text-wrap: balance`

[Jonathan Kew]

As of Firefox 121, I intend to turn the CSS `text-wrap: balance`
property value on by default.

This was developed behind the layout.css.text-wrap-balance.enabled
preference in https://bugzilla.mozilla.org/show_bug.cgi?id=1731541.

Status in other browsers is:
Chrome - supported since v114
Safari - currently behind a flag in Safari Tech Preview

Bug to turn on by default:
https://bugzilla.mozilla.org/show_bug.cgi?id=1860446

Standard:
https://drafts.csswg.org/css-text-4/#text-wrap-shorthand

(The CSS properties relating to line wrapping are currently in flux, but
the specific value `text-wrap: balance` is already shipping in Chrome
and there is significant interest from authors. In due course we'll
restructure the `text-wrap`[1] and `white-space`[2] properties to
conform to the revised specification, but `text-wrap: balance` will
continue to work under the updated model.)

This feature was previously discussed in this "Intent to prototype" thread:
https://groups.google.com/a/mozilla.org/g/dev-platform/c/O0U9UuhK90o

- JK


[1] https://bugzilla.mozilla.org/show_bug.cgi?id=1758391
[2] https://bugzilla.mozilla.org/show_bug.cgi?id=1852478