Added docs for multi field conditions

Author: Hyperkid123

packages/react-renderer-demo/src/app/pages/renderer/condition.md

@@ -32,7 +32,54 @@ You can show a field only if it meets a condition:
 }
 ```
 
-`when` - is name of field where the value is stored, **always required!**
+`when` - is name of field where the value is stored, **always required!**. It can be either string `'field-name'` or array of strings `['field-1', 'field-2']`.
+
+#### OR condition. At least one condition must be met
+
+If either of of fields with name `a` and `b` will have value `x` condition is met.
+
+```jsx
+{
+  fields: [{
+    name: 'Or condition',
+    component: 'text-field',
+    condition: {
+      when: ['a', 'b'],
+      is: 'x'
+    }
+  }]
+}
+```
+
+#### AND condition. All conditions must be met
+
+Field `controlled-field-1` must have value `Bar` and field `controlled-field-2` must include `FooBar` somewhere in its value to display field `BarFoo`.
+
+```jsx
+{
+  fields: [
+    {
+      name: 'controlled-field-1',
+      component: 'text-field',
+    },
+    {
+      name: 'controlled-field-2',
+      component: 'text-field',
+    } {
+      name: 'BarFoo',
+      label: 'Foo is Bar!',
+      component: 'text-field',
+      condition: [{
+        when: 'controlled-field-1',
+        is: 'Bar',
+      }, {
+        when: 'controlled-field-2',
+        pattern: /FooBar/
+      }],
+    },
+  ]
+}
+```
 
 ## Conditions