Make `WindowBuilder` `Send + Sync` #82

Job	Run time
Check formatting	18s
Run cargo-deny on Android	26s
Run cargo-deny on iOS	26s
Run cargo-deny on Linux	30s
Test stable Windows 64bit MSVC	2m 39s
Test stable Windows 32bit MSVC	2m 38s
Run cargo-deny on macOS	26s
Test stable Windows 64bit GNU	3m 31s
Run cargo-deny on Redox OS	26s
Test stable Windows 32bit GNU	2m 58s
Run cargo-deny on web	35s
Test stable Linux 32bit	6m 11s
Run cargo-deny on Windows	25s
Test stable Linux 64bit	4m 48s
Test stable X11	5m 11s
Test stable Wayland	2m 18s
Test stable Android	1m 54s
Test stable Redox OS	32s
Test stable macOS	2m 52s
Test stable iOS x86_64	2m 19s
Test stable iOS Aarch64	2m 13s
Test stable web	1m 19s
Test nightly Windows 64bit MSVC	2m 16s
Test nightly Windows 32bit MSVC	2m 58s
Test nightly Windows 64bit GNU	3m 54s
Test nightly Windows 32bit GNU	3m 11s
Test nightly Linux 32bit	5m 33s
Test nightly Linux 64bit	4m 57s
Test nightly X11	2m 28s
Test nightly Wayland	2m 31s
Test nightly Android	1m 20s
Test nightly Redox OS	25s
Test nightly macOS	2m 49s
Test nightly iOS x86_64	1m 24s
Test nightly iOS Aarch64	1m 25s
Test nightly web	1m 11s
Test 1.65.0 Windows 64bit MSVC	2m 31s
Test 1.65.0 Windows 32bit MSVC	3m 7s
Test 1.65.0 Windows 64bit GNU	3m 21s
Test 1.65.0 Windows 32bit GNU	3m 18s
Test 1.65.0 Linux 32bit	3m 19s
Test 1.65.0 Linux 64bit	2m 51s
Test 1.65.0 X11	2m 35s
Test 1.65.0 Wayland	2m 16s
Test 1.65.0 Redox OS	1m 53s
Test 1.65.0 macOS	3m 36s
Test 1.65.0 iOS x86_64	2m 27s
Test 1.65.0 iOS Aarch64	2m 17s
Test 1.65.0 web	2m 10s
Test 1.69.0 Android	1m 27s
	1h 58m 25s

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