errenous masking of windows message flags

[expikr]

capy/src/backends/win32/backend.zig

Line 1600 in c9e5ff8

if ((msg.message & 0xFF) == 0x012) { // WM_QUIT

This doesn't seem right, it will treat any message whose last byte matches 0x12 as quit, e.g. WM_HOTKEY, WM_EXITMENULOOP, WM_SYSCOMMAND, and those in the WM_USER + x ranges.