Poll the next pending event. Succeeds once with a dict for each
pending event, and fails when the queue is empty.
Event is a dict whose tag is the event type and which always contains
the keys type and timestamp. Additional type-specific keys are
present depending on the tag:
quit -- no extra keysmousemotion -- windowID, which, state, x, y, xrel, yrelmousebutton -- windowID, which, button, state, clicks, x, ykeyboard -- windowID, state, repeat, keysym
Only the event types handled by the binding are produced.
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@see https://wiki.libsdl.org/SDL3/SDL_PollEvent
