add option to set language with attribute

js/customElements/inline-code.js

 class InlineCode extends HTMLElement {
     constructor() {
         super();
-        this.innerHTML = "<code class=\"language-text\">" + this.innerHTML + "</code>";
+        const codeElement = document.createElement("code");
+        if (this.hasAttribute("language")) {
+            codeElement.classList.add(this.getAttribute("language"));
+        } else {
+            codeElement.classList.add("language-text");
+        }
+        codeElement.innerHTML = this.innerHTML;
+        this.appendChild(codeElement);
     }
 }