Emscripten samples

• ImGui Demo — Interactive Dear ImGui demonstration
• ImPlot Demo — Interactive ImPlot demonstration
• ImSpinner Demo — Interactive ImSpinner demonstration
• Yoga Playground — C++ implementation of Yoga Playground at yogalayout.com
• Taffy_cpp Playground — C++ implementation of Interactive Playground for Taffy/taffy_cpp similar to yogalayout.com
• FlatBuffers Compiler — Experimental demo: FlatBuffers schemas compiler, that runs in browser