Improve `har:view` refresh cycle

[nedtwigg]

Right now, when you do npm run har:view it looks like this if the dev server isn't running

Since hotreload doesn't seem to work, the current workflow is kinda painful

• kill the npm run dev
• restart npm run dev
• now refresh the page

A better flow might be this:

• the index page gives a warning IF the dev server is already running, it demands that the dev server should not be running
• the route that does the GET starts a dev server, and waits for it to finish before sending the content
  • if a dev server was already running, the GET kills it first
• if the hotreload isn't working at all for us, might be simpler to wire up to the prod builds instead....