It seems like webassembly in the browser is different enough of an architecture and use case that it makes sense that people would be designing languages designed from the bottom up to be compiled to it, but I can’t seem to find any.
Unlike Rust, which has excellent support for wasm output but wasn't created with wasm in mind, the above languages appear to have been created specifically with wasm as the native compile target.
Also, there's an excellent curated list of languages that compile to wasm:
The language isn't specifically built for web assembly but the framework is. But it allows the writing C# a traditionally server side language to run in the browser.
https://github.com/AssemblyScript/assemblyscript
https://github.com/FantasyInternet/poetry
https://github.com/ballercat/walt
https://github.com/MichaReiser/speedy.js
Unlike Rust, which has excellent support for wasm output but wasn't created with wasm in mind, the above languages appear to have been created specifically with wasm as the native compile target.
Also, there's an excellent curated list of languages that compile to wasm:
https://github.com/appcypher/awesome-wasm-langs