Support wasm-wasip1 target

[Master-Hash]

fix #407

Integration in browser see https://github.com/Wilfred/difftastic/issues/407#issuecomment-3576427850 Current difftastic doesn't support lib mode, so the module memory will be created everytime cli runs.

Already test binary locally.

Explanatory:

• The *.rs and Cargo.toml are from https://github.com/Elefunc/difftastic/commit/7cb1f966b0b7d0d49aed69eed3a7107e9f69f0ac
• Override rust toolchain version because of a target rename, I failed to build binary with old toolchain and old target name
• cross has poor support for wasi target, so I setup everything manually
• CI test not working, because ~~dev dep assert_cmd > wait-timeout only works on Windows and Unix~~ WASI forbids subprocess

[CetinSert]

Will maintain Elefunc's own web playground at dt.rt.ht/? ← has all the code.

Constantly improving: