Add Halton (although it's not supported at present)

lib/uk_planning_scraper/authorities.csv

@@ -63,6 +63,7 @@ St. Helens,https://publicaccess.sthelens.gov.uk/online-applications/search.do?ac
 Knowsley,https://planapp.knowsley.gov.uk/online-applications/search.do?action=advanced,england,merseyside,liverpoolcityregion
 Sefton,https://pa.sefton.gov.uk/online-applications/search.do?action=advanced,england,merseyside,liverpoolcityregion
 Wirral,https://planning.wirral.gov.uk/online-applications/search.do?action=advanced,england,merseyside,liverpoolcityregion
+Halton,https://webapp.halton.gov.uk/planningapps/,england,cheshire,liverpoolcityregion
 Sheffield,https://planningapps.sheffield.gov.uk/online-applications/search.do?action=advanced,england
 Wakefield,https://planning.wakefield.gov.uk/online-applications/search.do?action=advanced,england
 South Downs,https://planningpublicaccess.southdowns.gov.uk/online-applications/search.do?action=advanced,nationalparks,england