Refactor Saas naming, structure and modules

- Add more documentation.
- Use `main.scss` instead of importing components individually. This
  improves productivity without compilation errors due to missing
  imports and allows for easier future file/folder changes and
  refactorings inside `./styles`.
- Use partials with underscored naming. Because it documents that the
  files should not be individually imported.
- Introduce `third-party-extensions` folder to group styles that
  overwrites third party components.
- Refactor variable names from generic to specific.
- Use Sass modules (`@use` and `@forward`) over depreciated `@import`
  syntax.
- Separate font assets from Sass files (`styles/`). Create `assets/`
  folder that will contain both.
- Create `_globals.css` for global styling of common element instead of
  using `App.vue`.

src/presentation/assets/styles/_globals.scss

@@ -0,0 +1,25 @@
+/* 
+    Defines global styles that applies to globally defined tags by default (body, main, article, div etc.)
+*/
+
+@use "@/presentation/assets/styles/colors" as *;
+@use "@/presentation/assets/styles/fonts" as *;
+
+
+* {
+    box-sizing: border-box;
+}
+
+a {
+    color:inherit;
+    text-decoration: underline;
+    cursor: pointer;
+    &:hover {
+        color: $color-primary;
+    }
+}
+
+body {
+    background: $color-background;
+    font-family: $font-main;
+}