FEAT #11270 TIME 2:30 addd var lang + end front admin custom fields

...n/customField/custom-fields-administration.component.html

...n/customField/custom-fields-administration.component.scss

...ion/customField/custom-fields-administration.component.ts

src/frontend/lang/lang-en.ts

src/frontend/lang/lang-fr.ts

src/frontend/lang/lang-nl.ts