Only supported for plugins that set is_vector() to true. This returns
the frames as Gfx::VectorGraphics, which allows painting/rasterizing
them with arbitrary transforms and scales.
This adds a decoder for the TinyVG vector format (https://tinyvg.tech/).
TinyVG is a very simple binary vector format, but it is good enough to
represent a lot of SVGs, without needing the full web engine.
The main use case for Serenity is for scalable icons (which .tvg easily
handles).
