feat: add serde for NumHash #3913

Job	Run time
clippy	38s
cfg-check	23s
docs	1m 2s
check no_std	26s
doctest	1m 18s
feature-checks	3m 13s
fmt	12s
wasm-unknown	56s
test ubuntu-latest stable --no-default-features	1m 11s
wasm-wasi	1m 15s
test ubuntu-latest stable	1m 37s
test ubuntu-latest stable --all-features	2m 8s
test ubuntu-latest nightly --no-default-features	1m 14s
test ubuntu-latest nightly	1m 26s
test ubuntu-latest nightly --all-features	2m 8s
test ubuntu-latest 1.79 --no-default-features	41s
test ubuntu-latest 1.79	50s
test windows-latest stable --no-default-features	4m 20s
test windows-latest stable	4m 23s
test windows-latest stable --all-features	6m 15s
test windows-latest nightly --no-default-features	3m 31s
test windows-latest nightly	4m 24s
test windows-latest nightly --all-features	4m 29s
test windows-latest 1.79 --no-default-features	2m 22s
test windows-latest 1.79	2m 27s
	52m 49s

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