Offer a fallback for in-browser use?

Hello keyring maintainers 👋 

What would you think about offering a fallback backend when keyring is run in a browser (via pyodide/emscripten/wasm)? Does it make sense? The question was raised there: https://github.com/emscripten-forge/recipes/issues/5226#issuecomment-4250354271 for context