refactor: move encode HTML function into separate module (#4591)

Co-authored-by: Alexandr <qwerty541zxc@gmail.com>

src/common/html.js

@@ -0,0 +1,19 @@
+// @ts-check
+
+/**
+ * Encode string as HTML.
+ *
+ * @see https://stackoverflow.com/a/48073476/10629172
+ *
+ * @param {string} str String to encode.
+ * @returns {string} Encoded string.
+ */
+const encodeHTML = (str) => {
+  return str
+    .replace(/[\u00A0-\u9999<>&](?!#)/gim, (i) => {
+      return "&#" + i.charCodeAt(0) + ";";
+    })
+    .replace(/\u0008/gim, "");
+};
+
+export { encodeHTML };