jiff: add robust WASM support #311

Job	Run time
msrv	1m 47s
cross (i686-unknown-linux-gnu)	2m 23s
test (stable, ubuntu-latest, stable)	3m 3s
rustfmt	12s
cross (aarch64-unknown-linux-gnu)	2m 30s
test (beta, ubuntu-latest, beta)	3m 15s
testbench	1m 6s
cross (powerpc-unknown-linux-gnu)	2m 43s
test (nightly, ubuntu-latest, nightly)	2m 42s
wasm32-unknown-emscripten	2m 9s
cross (powerpc64-unknown-linux-gnu)	2m 36s
test (macos, macos-latest, stable)	2m 38s
cross (s390x-unknown-linux-gnu)	2m 21s
wasm32-unknown-uknown	42s
test (win-msvc, windows-latest, stable)	3m 30s
wasm32-wasip1	1m 59s
test (win-gnu, windows-latest, stable-x86_64-gnu)	3m 34s
	39m 10s

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