Fix WASM build

[fjarri]

• Add a CI step to test building on the WASM target
• Add the RNG parameter to Round::verify_message(). Fixes #105

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 90.15%. Comparing base (17de853) to head (91a3ae9).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #137 +/- ## ========================================== + Coverage 90.13% 90.15% +0.01% ========================================== Files 43 43 Lines 7737 7759 +22 ========================================== + Hits 6974 6995 +21 - Misses 763 764 +1 ```

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