added theme + icons

dsfr/artwork/background/ovoid.svg

dsfr/artwork/dark.svg

dsfr/artwork/light.svg

dsfr/artwork/pictograms/buildings/city-hall.svg

dsfr/artwork/pictograms/buildings/factory.svg

dsfr/artwork/pictograms/buildings/house.svg

dsfr/artwork/pictograms/buildings/nuclear-plant.svg

dsfr/artwork/pictograms/buildings/school.svg

dsfr/artwork/pictograms/digital/application.svg

dsfr/artwork/pictograms/digital/avatar.svg

dsfr/artwork/pictograms/digital/calendar.svg

dsfr/artwork/pictograms/digital/coding.svg

dsfr/artwork/pictograms/digital/data-visualization.svg

dsfr/artwork/pictograms/digital/internet.svg

dsfr/artwork/pictograms/digital/mail-send.svg

dsfr/artwork/pictograms/digital/search.svg

dsfr/artwork/pictograms/document/contract.svg

dsfr/artwork/pictograms/document/document-add.svg

dsfr/artwork/pictograms/document/document-download.svg

dsfr/artwork/pictograms/document/document-signature.svg