Markdown fixes (#321)

* Update packages

* Correctly escape code blocks. Fixes #316

* Wait, why?

* Support shell sessions

lib/markdown-renderer.js

@@ -11,24 +11,29 @@
  * limitations under the License.
  */
 import { Renderer } from 'marked';
+import { escape } from 'marked/src/helpers';
 import Prism from 'prismjs';
+import 'prismjs/components/prism-shell-session';
 
 export function createRenderer() {
   const renderer = new Renderer();
-  renderer.code = (code, infostring, escaped) => {
-    // We don’t have syntax highlighting for shell, but we use it in our
-    // README.md. This is a workaround so that rendering teh README.md
-    // succeeds and we can rip out the first paragraph.
+  renderer.code = (code, infostring) => {
+    // Aliasing sh, as that's common on github
     if (infostring === 'sh') {
-      infostring = '';
+      infostring = 'shell-session';
     }
-    if (!infostring || infostring.length <= 0) {
+
+    if (!infostring) {
       return `
-        <pre class="language-text"><code class="language-text">${code}</code></pre>`;
+        <pre class="language-text"><code class="language-text">${escape(
+          code,
+        )}</code></pre>`;
     }
+
     if (!(infostring in Prism.languages)) {
       throw Error(`Unsupported language "${infostring}"`);
     }
+
     return `
       <pre class="language-${infostring}"><code class="language-${infostring}">${Prism.highlight(
       code,