update packages and add valign

scripts/reveal.js/plugin/math/mathjax4.js

@@ -0,0 +1,81 @@
+/**
+ * A plugin which enables rendering of math equations inside
+ * of reveal.js slides. Essentially a thin wrapper for MathJax 4
+ *
+ * @author Hakim El Hattab
+ * @author Gerhard Burger
+ * @author Khris Griffis, Ph.D.
+ */
+export const MathJax4 = () => {
+
+    // The reveal.js instance this plugin is attached to
+    let deck;
+
+    let defaultOptions = {
+        tex: {
+            inlineMath: [ [ '$', '$' ], [ '\\(', '\\)' ]  ]
+        },
+        options: {
+            skipHtmlTags: [ 'script', 'noscript', 'style', 'textarea', 'pre', 'code' ]
+        },
+        startup: {
+            ready: () => {
+                MathJax.startup.defaultReady();
+                MathJax.startup.promise.then(() => {
+                    deck.layout();
+                });
+            }
+        }
+    };
+
+    function loadScript( url, callback ) {
+
+        let script = document.createElement( 'script' );
+        script.type = 'text/javascript';
+        script.id = 'MathJax-script';
+        script.src = url;
+        script.async = true;
+
+        // Wrapper for callback to make sure it only fires once
+        script.onload = () => {
+            if (typeof callback === 'function') {
+                callback.call();
+                callback = null;
+            }
+        };
+
+        document.head.appendChild( script );
+    }
+
+    return {
+        id: 'mathjax4',
+        init: function(reveal) {
+
+            deck = reveal;
+
+            let revealOptions = deck.getConfig().mathjax4 || {};
+            let options = { ...defaultOptions, ...revealOptions };
+            options.tex = { ...defaultOptions.tex, ...revealOptions.tex };
+            options.options = { ...defaultOptions.options, ...revealOptions.options };
+            options.startup = { ...defaultOptions.startup, ...revealOptions.startup };
+
+            let url = options.mathjax || 'https://cdn.jsdelivr.net/npm/mathjax@4/tex-mml-chtml.js';
+            options.mathjax = null;
+
+            window.MathJax = options;
+
+            loadScript(url, function() {
+                // MathJax 4.0.0 uses async startup, so we need to wait for it to be ready
+                MathJax.startup.promise.then(() => {
+                    // Initial typeset after startup
+                    MathJax.typeset();
+
+                    // Reprocess equations in slides when they turn visible
+                    deck.addEventListener('slidechanged', function(event) {
+                        MathJax.typeset();
+                    });
+                });
+            });
+        }
+    };
+};