perf: improve live reload performance

[mhanberg]

The way that live reload paths were being handled were creating some false
positives which then creating an infinite reload loop.

This required a change to web_dev_utils and then then a change to my sites reloader opts, the patterns
were not prefixed by ^. This will be updated in the tableau_new generator.

config :tableau, :reloader,
  patterns: [
    ~r"^lib/.*.ex",
    ~r"^(_posts|_docs)/.*.md",
    ~r"^(_includes)/.*.html",
    ~r"^assets/*.(css|js)"
  ]

This also changes it that websocket connections will not trigger a rebuild.