feat: Render undefined if value doesn't exist. Added codify test file

Author: kevinwang5658

package.json

@@ -36,6 +36,7 @@
   "scripts": {
     "start": "ts-node-esm src/demo/overview.tsx",
     "demo:overview": "tsx src/demo/overview.tsx",
+    "demo:codify": "tsx src/demo/codify.tsx",
     "demo:packagejson": "tsx src/demo/packagejson.tsx",
     "demo:custommanager": "tsx src/demo/custommanager.tsx",
     "demo:imperative": "tsx src/demo/imperative.ts",

src/FormFieldRenderer.tsx

@@ -61,7 +61,7 @@ export const FormFieldRenderer: React.FC<FormFieldRendererProps<any>> = props =>
             {props.field.required && <Text color="red">*</Text>}
             <Text>: </Text>
             <Text dimColor>
-              <RenderValue value={props.value as any} field={props.field} />
+              <RenderValue value={props.value as any ?? '<undefined>'} field={props.field} />
             </Text>
           </Text>
         </Box>

src/demo/codify.tsx

@@ -0,0 +1,51 @@
+import { render } from 'ink';
+import { Form } from '../Form.js';
+import React from 'react';
+
+const options = [
+  {label: 'Millenium Falcon', value: 'falcon'},
+  {label: 'TIE Advanced X1', value: 'tieadv'},
+  {label: 'X-Wing', value: 'xwing'},
+  {label: 'Raizorcrest', value: 'mando'},
+];
+
+render(
+  <Form
+    onSubmit={value => console.log(`Submitted: `, value)}
+    form={{
+      title: "Form title",
+      sections: [
+        {
+          title: "asdf-global",
+          fields: [
+            { type: 'string', name: 'plugin', label: 'plugin', required: true },
+            { type: 'string', name: 'version', label: 'version', required: true },
+          ]
+        },
+        {
+          title: "asdf-install",
+          fields: [
+            { type: 'string', name: 'directory', label: 'directory', required: true },
+          ]
+        },
+        {
+          title: "asdf-local",
+          fields: [
+            { type: 'string', name: 'plugin', label: 'plugin', required: true },
+            { type: 'string', name: 'version', label: 'version', required: true },
+            { type: 'string', name: 'directory', label: 'directory' },
+            { type: 'string', name: 'directories', label: 'directories' },
+          ]
+        },
+        {
+          title: "asdf-plugin",
+          fields: [
+            { type: 'string', name: 'plugin', label: 'plugin', required: true },
+            { type: 'string', name: 'versions', label: 'version'},
+            { type: 'string', name: 'gitUrl', label: 'plugin' },
+          ]
+        },
+      ]
+    }}
+  />
+);