Tighten notebook code cell output sandbox and enable it by default (#664)

* Tighten notebook code cell output sandbox

* Enable sandboxnotebookoutputs by default

* Address feedback

src/Explorer/Notebook/NotebookRenderer/outputs/SandboxJavaScript.tsx

@@ -0,0 +1,26 @@
+import { Media } from "@nteract/outputs";
+import React from "react";
+
+interface Props {
+  /**
+   * The JavaScript code that we would like to execute.
+   */
+  data: string;
+  /**
+   * The media type associated with our component.
+   */
+  mediaType: "text/javascript";
+}
+
+export class SandboxJavaScript extends React.PureComponent<Props> {
+  static defaultProps = {
+    data: "",
+    mediaType: "application/javascript",
+  };
+
+  render(): JSX.Element {
+    return <Media.HTML data={`<script>${this.props.data}</script>`} />;
+  }
+}
+
+export default SandboxJavaScript;