Add experimental libei support #306

Job	Run time
ci (stable, ubuntu-latest, --features default)	5m 15s
ci (stable, ubuntu-latest, --all-features)	6m 3s
ci (stable, windows-latest, --features default)	2m 31s
ci (stable, windows-latest, --all-features)	3m 0s
ci (stable, macos-latest, --features default)	5m 59s
ci (stable, macos-latest, --all-features)	46s
ci (nightly, ubuntu-latest, --features default)	5m 14s
ci (nightly, ubuntu-latest, --all-features)	7m 17s
ci (nightly, windows-latest, --features default)	3m 22s
ci (nightly, windows-latest, --all-features)	3m 23s
ci (nightly, macos-latest, --features default)	7m 58s
ci (nightly, macos-latest, --all-features)	4m 41s
ci (1.71.0, ubuntu-latest, --features default)	2m 7s
ci (1.71.0, ubuntu-latest, --all-features)	4m 3s
ci (1.71.0, windows-latest, --features default)	2m 41s
ci (1.71.0, windows-latest, --all-features)	2m 48s
ci (1.71.0, macos-latest, --features default)	3m 28s
ci (1.71.0, macos-latest, --all-features)	6m 51s
ci (ubuntu-latest, --features libei)	2m 7s
ci (ubuntu-latest, --features wayland)	2m 55s
ci (ubuntu-latest, --features xdo)	1m 25s
ci (ubuntu-latest, --features x11rb)	2m 2s
	1h 25m 56s

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