Add note about exception handling

Co-authored-by: Hood Chatham <[email protected]>

Author: juntyr

src/doc/rustc/src/platform-support/wasm32-unknown-emscripten.md

@@ -141,3 +141,8 @@ Please refer to the [`wasm32-unknown-unknown`](./wasm32-unknown-unknown.md)
 target's documentation on which WebAssembly features Rust enables by default, how
 features can be disabled, and how Rust code can be conditionally compiled based on
 which features are enabled.
+
+Note that Rust code compiled for `wasm32-unknown-emscripten` currently enables
+`-fexceptions` (JS exceptions) by default unless the Rust code is compiled with
+`-Cpanic=abort`. `-fwasm-exceptions` (WASM exceptions) is not yet currently supported,
+see <https://github.com/rust-lang/rust/issues/112195>.