Improve JS loading

[timacdonald]

Removing Prism.js

Before we moved to Torchlight we were using Prism.js to do highlighting.

We are still shipping Prism.js to the client even though we are not using it.

This means we ship ~20KB less JS to the client.

Removing unused vendor JS

• Removes the unused babel config.
• Removes the unused vendor/algoliasearch.js. We install this via NPM now.
• Removes the unused vendor/hogan.js. I don't even know what this is, but we don't use it anywhere I can see.
• Removes the unused vendor/typeahead.js. We don't seem to use this anywhere.

Additional build size improvements

app.js now builds to 157.34KB down from 169.14KB
docs.js now builds to 14.21KB down from 22.03KB
accessibility.js has been combined into docs.js to reduce the request count.

Overall reduction of ~22KB of JS.

Additional bundle loading improvements.

• Removes an additional asset request from the marketing pages.
• Removes an additional asset request from the docs pages.
• Makes a lazy request on the docs page eager, which should mean improved load times.
• Reorganizes the assets so that the marketing pages only load the JS they needs, i.e., it no longer loads the copy to clipboard, theming, and accessibility JS which are only used on the /docs pages.

[timacdonald]

These are loaded via docs.js as they are not needed on non-docs pages.