Capture # of connections opened per domain

[beenanner]

After more discussion in https://github.com/WPO-Foundation/tsproxy/issues/9 about failures. I was thinking we could capture total opened connection id counts per domain for analysis which could be beneficial. I know we can get this from the chrome logs not sure about firefox. We could possible use this to let a user know in coach that they are opening a lot of new connections and the load of a site could be affected by TCP slow start. They should reduce those to help with speeding up their page resources.