fix: send SDP answer if ICE gathering is taking long to complete

Fixes #68 (closed). Actually I'm not sure if it does fix that as there might be another reason of such behavior, but it fixes it for me.

TODO:

• We need to start the timeout after we get an SDP offer, not at begin.
• Before we forget, fix it in the Go version as well (or create an issue) (isn't this it snowflake#30498 ?)