Fixes #3929 Allow exporting functions named "default". #1977

Job	Run time
build_nightly	1m 46s
build_benchmarks	46s
build_examples	3m 47s
Check	53s
Verify that web-sys is compiled correctly	55s
dist_linux_aarch64_gnu	2m 44s
Clippy	6m 54s
dist_linux_x86_64_musl	2m 14s
dist_macos_x86_64	3m 47s
dist_windows	3m 9s
doc_api	1m 14s
dist_macos_aarch64	3m 38s
doc_book	6s
Rustfmt	8s
Build and test the deno example	45s
Run js-sys crate tests	2m 3s
Run native tests	2m 2s
Run UI compile-fail tests	44s
Test TypeScript output of wasm-bindgen	1m 12s
Run wasm-bindgen crate tests with multithreading enabled	1m 17s
Run wasm-bindgen crate tests (unix)	8m 32s
Run web-sys crate tests	6m 58s
Run wasm-bindgen-webidl crate tests	2m 4s
test_examples	1m 51s
deploy	32s
	1h 0m 1s

Provide feedback