Jetpack Cloud: Add Scan Error Page

[enejb]

Changes proposed in this Pull Request

• This PR adds a basic Scan error page.
  See:

Testing instructions

• Load up jetpack cloud with npm run start-jetpack-cloud
• Go to http://jetpack.cloud.localhost:3000/scan/{siteSlug}?scan-state=error
• Does the page look lke you would expect.

This page doesn't take into account the if threats are already found.

[matticbot]

Test live: https://calypso.live/?branch=add/scan-error-page

[matticbot]

Here is how your PR affects size of JS and CSS bundles shipped to the user's browser:

Sections (~128 bytes added 📈 [gzipped])

name           parsed_size           gzip_size
jetpack-cloud       +527 B  (+0.2%)     +128 B  (+0.2%)

Sections contain code specific for a given set of routes. Is downloaded and parsed only when a particular route is navigated to.

Legend

What is parsed and gzip size?

Parsed Size: Uncompressed size of the JS and CSS files. This much code needs to be parsed and stored in memory.
Gzip Size: Compressed size of the JS and CSS files. This much data needs to be downloaded over network.

Generated by performance advisor bot at iscalypsofastyet.com.

[rcanepa]

Besides the translation/localization issue, everything looks fine.

[rcanepa]

I think we should translate this text.

[enejb]

I left the translation issue as it is since mostly likely it will change in the future. :S
So I didn't want to translators working on translating something that would most likely change.