Update README with Ubuntu usage instructions and additional information. #222

Job	Run time
Clippy	31s
Clang Tidy	10s
Clippy nightly (optional)	59s
Build+test (stable, ubuntu-24.04)	1m 45s
Build+test (stable, ubuntu-22.04)	1m 43s
Check for documentation errors	52s
Format	15s
Build+test (beta, ubuntu-24.04)	1m 46s
Miri	1m 14s
Build+test (beta, ubuntu-22.04)	1m 47s
Packaging	2m 32s
Build+test (nightly, ubuntu-24.04)	1m 46s
Build+test (nightly, ubuntu-22.04)	2m 7s
Valgrind	2m 9s
	19m 36s

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