Implement `RTCRtpSender.getCapabilities` method (#3737) #57

Job	Run time
Rustfmt	12s
Check	1m 7s
Clippy	5m 30s
Run wasm-bindgen crate tests with multithreading enabled	1m 41s
Run wasm-bindgen crate tests (unix)	7m 21s
build_benchmarks	1m 0s
build_examples	3m 58s
build_nightly	1m 37s
Verify that web-sys is compiled correctly	53s
dist_linux_aarch64_gnu	2m 48s
dist_linux_x86_64_musl	2m 32s
dist_macos_aarch64	2m 16s
dist_macos_x86_64	3m 12s
dist_windows	2m 46s
doc_api	1m 19s
doc_book	37s
Build and test the deno example	54s
Run js-sys crate tests	2m 13s
Run native tests	1m 43s
Test TypeScript output of wasm-bindgen	1m 27s
Run UI compile-fail tests	1m 21s
Run web-sys crate tests	4m 16s
Run wasm-bindgen-webidl crate tests	2m 8s
deploy	2m 25s
test_examples	1m 59s
	57m 15s

Provide feedback