Add d-code and d-math componenents. Needs styling.

components/d-math.js

@@ -0,0 +1,36 @@
+import katex from "katex";
+
+export const html = `
+<style>
+dt-math[block] {
+  display: block;
+}
+</style>
+`;
+
+export class Math extends HTMLElement {
+
+  constructor() {
+    super();
+
+    const options = {childList: true};
+    let observer = new MutationObserver( (mutations) => {
+      observer.disconnect();
+      this.renderComponent();
+      observer.observe(this, options);
+    })
+    // try a first render
+    this.renderComponent();
+    // listen for changes
+    observer.observe(this, options);
+  }
+
+  renderComponent() {
+    const displayMode = this.hasAttribute("block");
+    const options = { displayMode: displayMode };
+    const renderedMath = katex.renderToString(this.textContent, options);
+    this.innerHTML = html + renderedMath
+  }
+}
+
+customElements.define("d-math", Math);