fix(datachannel): send DataChannelOpen for pre-negotiated channels (closes #61)#70

nightness wants to merge 1 commit intowebrtc-rs:masterwebrtc-rs/rtc:masterfrom

Brainwires:fix/negotiated-datachannelBrainwires/webrtc-rs-rtc:fix/negotiated-datachannelCopy head branch name to clipboard