FE: linting rule @typescript-eslint/explicit-module-boundary-types. Files : WMBBOX, WMCOnstants, WMDrawMarker

follow-up of #281 (closed) (closed)

when running npm run lint, there are a lot of warnings now that should be fixed

this ticket is for rule: @typescript-eslint/explicit-module-boundary-types

When all warnings for this rule are fixed, remove the rule from .eslintrc (this will make linting throw an error for it again)