feat: `RlpNode::as_hash` #174

Job	Run time
docs	31s
feature-checks	42s
clippy	35s
fmt	14s
miri --no-default-features	4m 44s
miri	4m 43s
test stable --no-default-features	23s
miri --all-features	4m 42s
test stable	23s
test stable --all-features	50s
test beta --no-default-features	18s
test beta	17s
test beta --all-features	52s
test nightly --no-default-features	35s
test nightly	33s
test nightly --all-features	49s
test 1.79 --no-default-features	17s
test 1.79	21s
test 1.79 --all-features	29s
	22m 18s

Provide feedback