feat(website): add n3 popup to website

[spencercorwin]

Description of the Change

• Work-In-Progress: adding a popup to the legacy website that notifies the user that neo-one.io is for Neo Legacy and that N3 docs can be found at n3.neo-one.io
• The added package (reactjs-popup) broke the React Static build process, so this PR is actually just a demonstration. This needs to be implemented without the reactjs-popup package
• Also needed to remove some newer TypeScript language features in order to get the website to compile

How it looks:

Test Plan

To run the website locally in dev mode:

• Run rush compile-website-dev
• When that is done (is very quick) run rush run-website-dev, which takes several minutes to finish
• Then go to localhost:3000

Alternate Designs

See notes above.

Benefits

Clarity for users on which docs they are reading.

Possible Drawbacks

Applicable Issues

#2511 #2410