Bump govuk_frontend_toolkit to 4.18.4
Bump govuk_frontend_toolkit to 4.18.4

https://raw.githubusercontent.com/alphagov/govuk_frontend_toolkit/master
/CHANGELOG.md

- Lint codebase using standard
- Add semicolons at the start of IIFE's

alphagov/govuk_elements,alphagov/govuk_elements,alphagov/govuk_elements,alphagov/govuk_elements