Todd Spangler NY Digital EditorIMDb TV, Amazon’s free-streaming video service, has ratcheted up its spending on original content — and more broadly, the e-commerce giant is trying to make the case to Madison Avenue that it has amassed a huge audience for ad-supported video content.At Amazon’s first NewFronts presentation for advertisers Monday, IMDb TV announced unscripted series with country star Luke Bryan and famed interior designer Jeff Lewis (“Flipping Out”).