Update doc.js

Author: thisunravisara

src/doc.js

@@ -150,6 +150,9 @@ var prototype = node.derive({
                         baseline: line.baseline,
                         left,
                         content: {
+                            // replace( /&(?!#?[a-z0-9]+;)/, '&' ) is to replace ampersand char with '&'
+                            // as  `&` can't be rendered in an SVG text
+                            // The regex explainer https://regex101.com/r/4vhX9N/1
                             text: text.run.text.trim().replace( /&(?!#?[a-z0-9]+;)/, '&' ) + ' '.repeat( word.space.length ),
                             size: text.run.size || this.defaultFormatting.size,
                             font: text.run.font || this.defaultFormatting.font,