Address warnings

[raclim]

Changes:

• removes SASS warnings when using division
• removes required prop-type warning in routes.jsx
• adds aria labels to LoginForm.jsx and SignupForm.jsx and corrects semantic html for the containers of the label and input fields

I have verified that this pull request:

• has no linting errors (npm run lint)
• has no test errors (npm run test)
• is from a uniquely-named feature branch and is up to date with the develop branch.
• is descriptively named and links to an issue number, i.e. Fixes #123

[release-com]

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• p5.js-web-editor
  • app-ted4766.release.editor.p5js.org/
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🔧Environment Status : https://app.release.com/public/Processing%20Foundation/env-4f956f0d8c