jiff: add robust WASM support #303

Job	Run time
wasm32-wasip1	1m 26s
test (stable, ubuntu-latest, stable)	7m 14s
test (beta, ubuntu-latest, beta)	7m 25s
msrv	1m 29s
rustfmt	13s
test (nightly, ubuntu-latest, nightly)	6m 17s
test (macos, macos-latest, stable)	6m 34s
testbench	58s
wasm32-unknown-emscripten	2m 9s
test (win-msvc, windows-latest, stable)	5m 35s
test (win-gnu, windows-latest, stable-x86_64-gnu)	8m 16s
wasm32-unknown-uknown	25s
	48m 1s

Provide feedback