feat: Add `Builder::permissions()` method. #195

Job	Run time
WASI Test Build	16s
Clippy and fmt	7s
Cargo deny (ubuntu-latest)	19s
OS Test (nightly, ubuntu-latest)	13s
WASM Test Build	6s
OS Test (nightly, windows-latest)	30s
OS Test (nightly, macos-latest)	31s
OS Test (stable, ubuntu-latest)	13s
OS Test (stable, windows-latest)	1m 21s
OS Test (stable, macos-latest)	23s
OS Test (1.63, ubuntu-latest)	2m 46s
OS Test (1.63, windows-latest)	3m 38s
OS Test (1.63, macos-latest)	5m 20s
	15m 43s

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