fix(date): implements Validator

CHANGELOG.md

...x-dsfr-components/src/lib/patterns/date/date.component.ts

...-dsfr-components/src/lib/patterns/date/date.model.spec.ts

...s/ngx-dsfr-components/src/lib/patterns/date/date.model.ts

.../lib/patterns/date/demo/demo-date-reactive.component.html

...rc/lib/patterns/date/demo/demo-date-reactive.component.ts

.../src/lib/patterns/date/demo/demo-date-reactive.stories.ts

...rc/lib/shared/components/demo/demo-toolbar.component.html

.../src/lib/shared/components/demo/demo-toolbar.component.ts