- Upgrades cssnano to 1.2.0
- Only removes whitespaces from downloaded font declarations
- Disables Font optimization for AMP pages

This PR replaces `prop-types-exact` (only used in this location) with manual property checking.

Right now, malformed properties sent to `<Link>` are silently handled and only emit a warning in the console.
This leads to confusing/unexpected errors because we try to read a value that is undefined.

To fix this, we'll now throw a proper error when `<Link>` is misused. **This still isn't optimal, however, because we don't have a component stack trace we can give the user**.
We're not going to be able to give the user actionable instructions until React 16.14 at a minimum.

---

Fixes #13951
Fixes #16107
Closes #13962

Co-authored-by: NTim Neutkens <timneutkens@me.com>
Co-authored-by: Nkodiakhq[bot] <49736102+kodiakhq[bot]@users.noreply.github.com>

**What's the problem this PR addresses?**

https://github.com/vercel/next.js/pull/16048 stopped bundling `caniuse-lite` but didn't declare it as a dependency

https://github.com/yarnpkg/berry/runs/972037981?check_suite_focus=true#step:5:75

**How did you fix it?**

Add `caniuse-lite` as a dependency

---
cc @Timer 

As mentioned in https://github.com/vercel/next.js/issues/14157#issuecomment-667328984 I looked into adding a PnP e2e test but the use of the `gist` protocol stopped me from getting it to work since v2 doesn't support that yet. Would it be possible to change this to one of the supported protocols (https://yarnpkg.com/features/protocols)?
https://github.com/vercel/next.js/blob/636672755004c756eefcddb5d4ccabbc1855e75a/packages/next/package.json#L208

See [release notes](https://github.com/ampproject/amp-toolbox/releases/tag/v2.6.0).

**Highlight:** [hero images can now be server-side rendered](https://github.com/ampproject/amp-toolbox/tree/main/packages/optimizer#preloadheroimage) by annotating then with `data-hero`. This will greatly improves LCP when using large images in the first viewport.

```
<amp-img data-hero src="/hero.jpg" layout="responsive" width="640" height="480"></amp-img>
```

Also fixes #15979