Adds support for using hifitime in WASM targets #422

Job	Run time
Check	17s
Lints	54s
Coverage	39s
Test Suite (ubuntu-latest, MSRV)	3m 2s
no-std build (aarch64-unknown-none)	24s
Test Suite (ubuntu-latest, stable)	2m 45s
no-std build (thumbv6m-none-eabi)	20s
Test Suite (macos-latest, MSRV)	6m 40s
Test Suite (macos-latest, stable)	5m 3s
Test Suite (windows-latest, MSRV)	8m 50s
Test Suite (windows-latest, stable)	9m 42s
Release	0s
	38m 36s

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