Listen for browser paste events and directly inject clipboard text via
AddInputCharactersUTF8. Also suppress character input when Ctrl/Meta is
held to prevent 'v' from being typed on Cmd+V.
The Emscripten backend was missing Platform_SetClipboardTextFn/GetClipboardTextFn,
so ImGui::SetClipboardText was a no-op in the browser.
Hook navigator.clipboard.writeText for writes and keep a local copy for reads.
ImGui OpenGL loader is patched, and not regenerated, because the gl3w
script requires network connectivity to download the header files from
Khronos at build time.
Bartosz Taudul
DaniPopes