docs: Update fields examples in README (#396)

README.md

@@ -346,24 +346,34 @@ The stream API can also work on object mode. This is useful when you have an inp
 ```js
 {
   fields: [
+    // Supports pathname -> pathvalue
+    'simplepath', // equivalent to {value:'simplepath'}
+    'path.to.value' // also equivalent to {value:'path.to.value'}
+
     // Supports label -> simple path
     {
-      label: 'some label', // (optional, column will be labeled 'path.to.something' if not defined)
+      label: 'some label', // Optional, column will be labeled 'path.to.something' if not defined)
       value: 'path.to.something', // data.path.to.something
-      default: 'NULL' // default if value is not found (optional, overrides `defaultValue` for column)
+      default: 'NULL' // default if value is not found (Optional, overrides `defaultValue` for column)
     },
 
     // Supports label -> derived value
     {
-      label: 'some label', // Supports duplicate labels (required, else your column will be labeled [function])
-      value: (row, field) => row.path1 + row.path2, // field = { label, default }
+      label: 'some label', // Optional, column will be labeled with the function name or empty if the function is anonymous
+      value: (row, field) => row[field.label].toLowerCase() ||field.default,
       default: 'NULL', // default if value function returns null or undefined
-      stringify: true // If value is function use this flag to signal if resulting string will be quoted (stringified) or not (optional, default: true)
     },
 
-    // Support pathname -> pathvalue
-    'simplepath', // equivalent to {value:'simplepath'}
-    'path.to.value' // also equivalent to {value:'path.to.value'}
+    // Supports label -> derived value
+    {
+      value: (row) => row.arrayField.join(',')
+    },
+
+    // Supports label -> derived value
+    {
+      value: (row) => `"${row.arrayField.join(',')}"`,
+      stringify: false // This flag signals if the resulting string should be quoted (stringified) or not (optional, default: true)
+    },
   ]
 }
 ```