Mostly implement dark mode

README.md

index.html

src/components/forms/FormInput.tsx

src/components/forms/FormSelect.tsx

src/components/i18n/lang/de.json

src/components/i18n/lang/en.json

src/components/layout/App.tsx

src/components/layout/Header.tsx

src/components/layout/MobileNavigation.tsx

src/components/layout/Navigation.tsx

src/components/pages/ContactPage.tsx

src/components/pages/DiscordLinkPage.tsx

src/components/pages/IndexPage.tsx

src/components/shells/Shells.tsx

src/components/shells/ThemeShell.tsx

src/components/widgets/Button.tsx

src/components/widgets/HR.tsx

src/components/widgets/LanguageSelect.tsx

src/components/widgets/LoadingIndicator.tsx

src/components/widgets/TextLink.tsx