feat: front-end for new authentication system

[KaWaite]

Overview

The new authentication system will allow developers to use built-in log in, sign up, and reset password pages. This is the basic foundation + log in page.

What I've done

• New RootPage that shows a loader before redirecting the user to the login page url specified on the back-end.
• Log in page
• Removed TopPage files

What I haven't done

• No Signup page
• No Reset page
• Log in page has links to both signup and reset pages and Re:Earth's back-end isn't setup for using the Login page yet so the Login component is commented out

Screenshot

[netlify]

✔️ Deploy Preview for reearth-web ready!

🔨 Explore the source changes: 86986bc

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[codecov]

Codecov Report

Merging #102 (86986bc) into main (bea1a32) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #102   +/-   ##
=======================================
  Coverage   53.53%   53.53%           
=======================================
  Files          48       48           
  Lines         891      891           
  Branches      119      119           
=======================================
  Hits          477      477           
  Misses        364      364           
  Partials       50       50           

Impacted Files	Coverage Δ
src/theme/darkTheme.ts	100.00% <ø> (ø)
src/theme/lightheme.ts	100.00% <ø> (ø)
src/theme/theme.ts	100.00% <ø> (ø)

[HideBa]

I've left a couple of comments.
Plz have a look. Mostly fine!

[rot1024]

• Tweak the gradient color of background of login page
• Will implementation of sign up and password reset screen be done in another PR?

[HideBa]

LGTM