docs(operators): add documentation for toPromise

src/operator-docs/utility/toPromise.ts

@@ -1,6 +1,46 @@
 import { OperatorDoc } from '../operator.model';
 
-export const toPromise: OperatorDoc = {
-  'name': 'toPromise',
-  'operatorType': 'utility'
+export const toPromiseOperator: OperatorDoc = {
+  name: 'toPromise',
+  operatorType: 'utility',
+  signature: 'public toPromise(PromiseCtor: *): Promise<T>',
+  parameters: [
+    {
+      name: 'PromiseCtor',
+      type: '*',
+      attribute: 'optional',
+      description: `promise The constructor of the promise. If not provided,
+        it will look for a constructor first in Rx.config.Promise then fall back to the native Promise constructor if available.`
+    }
+  ],
+  shortDescription: {
+    description: `An ES2015 compliant promise which contains the last value from the Observable sequence.
+      If the Observable sequence is in error, then the Promise will be in the rejected stage.
+      If the sequence is empty, the Promise will not resolve.`,
+    extras: [
+      {
+        type: 'Tip',
+        text:
+          'This operator makes reactive programming easy to use for developers who are not used to it.'
+      }
+    ]
+  },
+  examples: [
+    {
+      name: 'Just return the emitted value of the observable as a promise',
+      code: `
+          const source = Rx.Observable
+            .of(42)
+            .toPromise();
+
+        source.then((value) => console.log('Value: %s', value));
+        // => Value: 42
+      `,
+      externalLink: {
+        platform: 'JSBin',
+        url: 'http://jsbin.com/fanivejahe/embed?js,console,output'
+      }
+    }
+  ],
+  relatedOperators: ['map', 'subscribe']
 };