implement hash concat for wasm pkg

Changes

[X] An issue to be fixed by this PR is listed above.
[ ] New tests are added to ensure new features are working. Please refer to this page to see how to add a test.
[ ] ./frb_internal precommit --mode slow (or fast) is run (it internal runs code generator, does auto formatting, etc).
[ ] If this PR adds/changes features, documentations (in the ./website folder) are updated.
[ ] CI is passing. Please refer to this page to see how to solve a failed CI.

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