Quality of Life improvements

Changelog

• The README.md has been adjusted to further improve the corporate branding and provide information about Material Design for Bootstrap (MDB React) Pro.
• The src/public/index.html file has been improved regarding preperations for implementation of the favicons.
• The in-code documentation has been improved in multiple files.
• The SCSS of the HomePage component is no longer being loaded in the src/index.scss - but is now loaded directly in the component as intended.
• The enviroment variables .env have been included in the .gitignore which should reduce the risk of pushing it to GitHub unintentionally.
• The gh-pages npm package has been added in preperation to active deployment to GitHub-Pages.
• The npm package react is no longer mentioned two times under devDependencies in the package.json file.