Update socket.io to v3.x and allow interop with existing socket.io implementations

[chrismatthieu]

No description provided.

[vincentfretin]

See my comment there as well #235 (comment)
I'm in the process of reintegrating the easyrtc adapter in the repo, see #240 . Please wait for my easyrtc PR before doing any changes related to upgrading socket.to v3.
I see that open-easyrtc is still using "socket.io-client": "^2.2.0" in it's package.json. You may want to create an issue there as well. cc @hthetiot

[vincentfretin]

I'm now open to any PR that update socket.io. I'm not going to work on it myself, please contribute.
Places that needs to be updated:

• link in all the examples, docs/getting-started-local.md, README.md
• update socket.io in package.json and package-lock.json
• update open-easyrtc to a version that supports socketio v3
• adapt server/easyrtc-server.js and server/socketio-server.js to new socketio api
• adapt src/adapters/EasyRtcAdapter.js and src/adapters/WsEasyRtcAdapter.js if necessary
• add a commented example or good default to configure cors origins in server/easyrtc-server.js and server/socketio-server.js and explain it in the documentation

[hthetiot]

update open-easyrtc to a version that supports socketio v3

I will take care of this on open-easyrtc and notify here when available.

[vincentfretin]

Just adding a reference to open-easyrtc/open-easyrtc#70 as a first step.

[hthetiot]

Thank you @vincentfretin , it will be upgraded to socket.io V4 in fact :)