Add application-level ping pong

[lugehorsam]

• Allows the user to set a heartbeat interval between which the client pings and expects a pong in response. If the pong doesn't arrive, the socket calls ondisconnect. Most browsers natively do pinging and ponging, but Chrome doesn't (see https://bugs.chromium.org/p/chromium/issues/detail?id=706002).
• Adds send and connect timeouts to the socket.
• Cleans up a couple README.md commands for making builds.
• Cleans up Typescript errors in our test package that were found by tsc.
• Updates test dependencies.

It's not currently possible to write tests for this without some unsavory modifications to either the test runner or the client -- so I just tested using our index.html.

[tomglenn]

@lugehorsam LGTM. I wasn't able to run the test suite due to errors. I know these were previously failing and we've discussed they need updating separately, I just wasn't sure if the changes you'd made were expected to fix these or not.

[lugehorsam]

Hey @tomglenn yeah good question -- so they fixed some of the errors but I have found a couple others related to dependencies seeming to leak between workspaces. I was thinking I'd fix that in a separate PR if that makes sense to you.

[tomglenn]

@lugehorsam Yep cool that makes sense. 👍