Redesign the website and update the tutorials (#6)

A refresh of the FEAScript website, covering the home page, the Studio page and all 14 tutorials, plus fixes to the tutorial content and some search-engine improvements.

Author: nikoscham

.prettierrc

@@ -0,0 +1,4 @@
+{
+  "printWidth": 110,
+  "trailingComma": "all"
+}

README.md

@@ -6,6 +6,10 @@
 
 FEAScript is a finite element simulation library built in JavaScript. This is the source code of the FEAScript <a href="https://feascript.com/" target="_blank">website</a>.
 
+## Tutorial section labels
+
+Tutorial sections and subsections use `<div class="eyebrow label">` with a `<p>` for the title. Keep `role="heading"` and `aria-level="2"` or `aria-level="3"` to preserve heading navigation, and retain existing IDs and named anchors for section links. Level-two labels also supply the current section title in the sticky document bar.
+
 ## License
 
 The content of the FEAScript website is licensed under <a href="https://github.com/FEAScript/FEAScript-website/blob/main/LICENSE" target="_blank">CC-BY 4.0</a>. Note that the core library of FEAScript is distributed under the terms of the <a href="https://github.com/FEAScript/FEAScript-core/blob/main/LICENSE" target="_blank">MIT license</a>.