feat: add missing size fn #5153

Job	Run time
docs	1m 0s
check no_std	47s
clippy	1m 25s
doctest	1m 34s
feature-checks	2m 24s
fmt	15s
test ubuntu-latest stable --no-default-features	1m 31s
wasm-unknown	2m 21s
test ubuntu-latest stable	2m 22s
wasm-wasi	2m 21s
test ubuntu-latest stable --all-features	2m 22s
test ubuntu-latest nightly --no-default-features	1m 33s
test ubuntu-latest nightly	1m 10s
test ubuntu-latest nightly --all-features	1m 33s
test ubuntu-latest 1.79 --no-default-features	1m 35s
test ubuntu-latest 1.79	1m 32s
test windows-latest stable --no-default-features	2m 14s
test windows-latest stable	2m 14s
test windows-latest stable --all-features	2m 15s
test windows-latest nightly --no-default-features	2m 14s
test windows-latest nightly	2m 15s
test windows-latest nightly --all-features	2m 16s
test windows-latest 1.79 --no-default-features	2m 8s
test windows-latest 1.79	2m 8s
ci success	4s
	43m 33s

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