add `obj` directory icon #1183

Job	Run time
Code Coverage (ubuntu-latest)	2m 26s
Style (ubuntu-latest)	4m 13s
Style (macos-latest)	5m 23s
MinSRV	1m 19s
Style (windows-latest)	7m 23s
Build (ubuntu-latest, arm-unknown-linux-gnueabihf, use-cross)	5m 5s
Build (ubuntu-latest, aarch64-unknown-linux-gnu, use-cross)	5m 28s
Build (ubuntu-latest, aarch64-unknown-linux-musl, use-cross)	6m 51s
Build (ubuntu-latest, i686-unknown-linux-gnu, use-cross)	6m 13s
Build (ubuntu-latest, i686-unknown-linux-musl, use-cross)	5m 0s
Build (ubuntu-latest, x86_64-unknown-linux-gnu, use-cross)	4m 46s
Build (ubuntu-latest, x86_64-unknown-linux-musl, use-cross)	4m 58s
Build (macos-latest, x86_64-apple-darwin)	5m 5s
Build (macos-latest, aarch64-apple-darwin)	3m 13s
Build (windows-latest, i686-pc-windows-gnu)	8m 8s
Build (windows-latest, i686-pc-windows-msvc)	11m 16s
Build (windows-latest, x86_64-pc-windows-gnu)	14m 42s
Build (windows-latest, x86_64-pc-windows-msvc)	10m 19s
	1h 51m 48s

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