added missed source code inspector files

src/SourceCodeInspector.js

@@ -0,0 +1,72 @@
+import React, { useEffect, useState } from "react";
+import defaultPropTypes from "./defaultPropTypes";
+import styles from "./SourceCodeInspector.module.css";
+import { nodePath } from "./nodeData";
+import ToggleablePanel from "./ToggleablePanel";
+
+const SourceCodePanel = (props) => {
+  const { node, state } = props;
+  const {
+    config: {
+      codeInspector: { prefix },
+    },
+  } = state;
+
+  const [code, setCode] = useState();
+
+  const path = nodePath(node);
+  const url = `${prefix}${path}`;
+
+  useEffect(() => {
+    async function fetchData() {
+      console.log(`fetching ${path} from ${url}`);
+      try {
+        const response = await fetch(url);
+        if (!response.ok) {
+          const text = `Error fetching URL ${url}\nHTTP response: ${response.status}:${response.statusText}`;
+          setCode(text);
+        } else {
+          const text = await response.text();
+          setCode(text);
+        }
+      } catch (ex) {
+        console.error("Exception caught:", ex);
+        if (ex.message.startsWith("NetworkError")) {
+          setCode(
+            `Network error talking to server\ntrying URL ${url}\nServer not found, or invalid CORS handling.`
+          );
+        } else {
+          throw ex;
+        }
+      }
+    }
+    fetchData();
+  }, [path, url]);
+
+  return code ? (
+    <pre className={styles.code}>
+      <code>{code}</code>
+    </pre>
+  ) : (
+    <p>loading</p>
+  );
+};
+
+SourceCodePanel.propTypes = defaultPropTypes;
+
+const SourceCodeInspector = (props) => {
+  const { node, state, dispatch } = props;
+  const { enabled } = state.config.codeInspector;
+
+  return enabled ? (
+    <ToggleablePanel title="Code" showInitially={false}>
+      <SourceCodePanel node={node} state={state} dispatch={dispatch} />
+    </ToggleablePanel>
+  ) : (
+    ""
+  );
+};
+
+SourceCodeInspector.propTypes = defaultPropTypes;
+
+export default SourceCodeInspector;

src/SourceCodeInspector.module.css

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+.code {
+    overflow:auto;
+    max-height: 500px;
+}