prefer-formatValues

Rejects multiple calls to document.l10n.formatValue in the same code block, to reduce localization overheads.

Examples of incorrect code for this rule:

{
  document.l10n.formatValue('foobar');
  document.l10n.formatValue('foobaz');
}

Examples of correct code for this rule:

document.l10n.formatValue('foobar');
document.l10n.formatValues(['foobar', 'foobaz']);