* Add initial AMP implementation

* Implement experimental feature flag

* Implement feedback from sbenz

* Add next/amp and `useAmp` hook

* Use /:path*/amp instead

* Add canonical

* Add amphtml tag

* Add ampEnabled for rel=“amphtml”

* Remove extra type

Changelog https://github.com/zeit/styled-jsx/releases/tag/v3.2.1

* Bring in terser-webpack-plugin

* Ignore terser from linting

* Implement circular JSON err.sh link

* Add test for getInitialProps returning circular json

* Make test warn less

* Fix tests

* Add reference to original tests

We want our new memory optimizations (https://github.com/webpack/webpack/pull/8609)

There's still a few Typescript helpers in use, but regenerator is added by Babel after this change, as it was already in the bundle it'll drop bundle sizes by quite a bit, eg _app.js becomes half the size.

Introduces full support for Babel 7 including JSX Fragments shorthand. 
Switched to visiting the `Program` path and then start a traversal manually to solve conflicts with other Babel plugins.

Continuation of #5945 

* Remove next/asset

Reasoning described in #5970

* Remove next/asset tests

* Bring back asset-page

Fixes parts of #5716. I had some issues with the test suite but I'm fairly certain that I got it working correctly.