extract-pot does not recognize format()

[clkao]

For example templates/country/dataset.html has

<p>{{format("On this page you can see the state of open data for %(dataset)s in all the places for which we have information.", { dataset: dataset.title}) }}</p>

This can't be localized as it's never in the po template.

[rufuspollock]

Moving to next-up as do not think this is urgent.

[clkao]

Depends on mozilla/i18n-abide#26 or implementing alternative build rules such as using gulp-xgettext for invoking jsxgettext properly.