Allow floating environments (figures, tables) to extend into margins

As discussed with @xdohnal and @xsvobod2 during today’s meeting, there is some interest in adding the option to increase \linewidth for floating environments (figures, tables), effectively allowing them to extend into the margins. I propose introducing this as an opt-in feature: disabled by default to maintain compatibility with existing documents, but enabled by default in the Overleaf template for new documents.