Add WASM support.

[mefyl]

This MR adds the required stubs for wasm_of_ocaml. They are simple no-ops.

[mefyl]

I'm very sorry but I can't make any sense of the output of the CI. I think it's unrelated to these changes, because it's about file permissions (or is it?). Yet it seems to be greener on master, so I'm just very confused.

File "test/e2e/alcotest/passing/only_monadic_effects-js.expected", line 1, characters 0-0:
/usr/bin/git --no-pager diff --no-index --color=always -u /dev/null _build/default/test/e2e/alcotest/passing/only_monadic_effects-js.processed
diff --git a/_build/default/test/e2e/alcotest/passing/only_monadic_effects-js.processed b/_build/default/test/e2e/alcotest/passing/only_monadic_effects-js.processed
new file mode 100644
index 0000000..e69de29
(cd _build/default/examples && /opt/hostedtoolcache/node/24.14.1/x64/bin/node floats.bc.js)