Add a default theme for unfocused Windows #6305

Job	Run time
📊 Static checks / Code style, file formatting, and docs	40s
🐧 Linux / Editor w/ Mono (target=editor)	4m 12s
🐧 Linux / Editor with doubles and GCC sanitizers (target=editor, tests=yes, dev_build=yes, scu_build=yes, precision=double, use_asan=yes, use_ubsan=yes, linker=gold)	25m 10s
🐧 Linux / Editor with clang sanitizers (target=editor, tests=yes, dev_build=yes, use_asan=yes, use_ubsan=yes, use_llvm=yes, linker=lld)	8m 19s
🐧 Linux / Template w/ Mono (target=template_release)	1m 15s
🐧 Linux / Minimal template (target=template_release, everything disabled)	1m 10s
🍎 macOS / Editor (target=editor, tests=yes)	6m 50s
🍎 macOS / Template (target=template_release)	3m 46s
🌐 Web / Template (target=template_release)	1m 33s
🏁 Windows / Editor (target=editor, tests=yes)	11m 49s
🏁 Windows / Template (target=template_release)	10m 28s
🤖 Android / Template (target=template_release)	5m 28s
🍏 iOS / Template (target=template_release)	3m 27s
	1h 24m 7s

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