Add en-GB localisation (#5952)

* Create blank en-GB/messages.po

* localise certain strings for en-GB

* Update lingui.config.js

* Update dates.ts

* Update helpers.ts

* Update i18n.ts

* Update i18n.web.ts

* Update languages.ts

* Update i18n.ts

src/locale/languages.ts

@@ -8,6 +8,7 @@ export enum AppLanguage {
   en = 'en',
   ca = 'ca',
   de = 'de',
+  en_GB = 'en-GB',
   es = 'es',
   fi = 'fi',
   fr = 'fr',
@@ -35,6 +36,7 @@ export const APP_LANGUAGES: AppLanguageConfig[] = [
   {code2: AppLanguage.en, name: 'English'},
   {code2: AppLanguage.ca, name: 'Català – Catalan'},
   {code2: AppLanguage.de, name: 'Deutsch – German'},
+  {code2: AppLanguage.en_GB, name: 'English (UK)'},
   {code2: AppLanguage.es, name: 'Español – Spanish'},
   {code2: AppLanguage.fi, name: 'Suomi – Finnish'},
   {code2: AppLanguage.fr, name: 'Français – French'},