- Load bundled TinyMCE i18n language file based on a
listmonk -> TinyMCE map.
- Refactor editor initialisation to accommodate this change.
- Introduce `constants.js -> uris.static` to make the static URI
available to TinyMCE for loading language files.
- Namespace all admin UI URLs behind `/admin/*`.
This breaks the current admin UI URLs.
- Make Vue output build assets to `frontend/dist/*` instead of
`frontend/dist/frontend`.
- Namespace Vue static assets to `/admin/static/*`.
This commit reduces the cofusing and convoluted Vue+WebPack build URI
and static path schemes. In addition, it removes ambiguity in URLs
where non-UI URLs like `/public`, `/api`, `/webhooks` etc. were in the
same name space as UI URLs like `/campaigns`, `/lists` etc. Now all UI
URLs are behind `/admin/`, also simplifying security rules for proxies.