Setup frontend styling

- Add node-sass, bootstrap and reactstrap
- Setup styles directory with themes file and base styles
- Replace create-react-app content with sample content to test styles

frontend/src/assets/styles/main.scss

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+@import "./theme.scss";
+
+// Core styles here...
+.App {
+    font-family: $primary-font;
+    color: $text-color-primary;
+    background-color: $background-color-primary;
+}

frontend/src/assets/styles/theme.scss

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+@import url('https://fonts.googleapis.com/css2?family=Poppins&display=swap');
+
+// COLOURS
+$background-color-primary: #000000;
+$text-color-primary: #ffffff;
+$biosphere-blue: #0071bcff;
+
+// FONTS
+$primary-font: 'Poppins', sans-serif;