Add additional duty expression formatting.
Add additional duty expression formatting.

alphagov/trade-tariff-frontend,bitzesty/trade-tariff-frontend,alphagov/trade-tariff-frontend,bitzesty/trade-tariff-frontend,bitzesty/trade-tariff-frontend,alphagov/trade-tariff-frontend,alphagov/trade-tariff-frontend,bitzesty/trade-tariff-frontend