docs(operators): add documentation for operator empty

Add initial version of documentation for creation operator 'empty'.

Author: grumblerchester

src/operator-docs/creation/empty.ts

@@ -1,6 +1,70 @@
 import { OperatorDoc } from '../operator.model';
 
 export const empty: OperatorDoc = {
-  'name': 'empty',
-  'operatorType': 'creation'
+  name: 'empty',
+  operatorType: 'creation',
+  signature: 'public empty<T>(scheduler?: IScheduler): Observable<T>',
+  parameters: [
+    {
+      name: 'scheduler',
+      type: 'IScheduler',
+      attribute: 'optional',
+      description:
+        'Allows scheduling the emission of the complete notification.'
+    }
+  ],
+  marbleUrl: 'http://reactivex.io/rxjs/img/empty.png',
+  shortDescription: {
+    description:
+      'Creates an Observable that emits no items to the Observer' +
+      ' and immediately emits a complete notification.'
+  },
+  walkthrough: {
+    description: `This static operator is useful for creating a simple
+       Observable that only emits the complete notification. It can be used for
+       composing with other Observables`
+  },
+  examples: [
+    {
+      name: 'Observable completes immediately',
+      code: `const observable = Rx.Observable.empty();
+             const subscription = observable.subscribe({
+               next: () => console.log('next'), // does not log anything
+               complete: () => console.log('complete'), // logs 'complete'
+             });`,
+      externalLink: {
+        platform: 'JSBin',
+        url: 'http://jsbin.com/hojacunecu/1/edit?js,console,output'
+      }
+    },
+    {
+      name: 'Observable emits initial value then completes',
+      code: `const observable = Rx.Observable.empty().startWith('initial value');
+             const subscription = observable.subscribe({
+               next: (val) => console.log(\`next: \${val}\`), // logs 'next: initial value'
+               complete: () => console.log('complete'), // logs 'complete'
+             });`,
+      externalLink: {
+        platform: 'JSBin',
+        url: 'http://jsbin.com/tubonoradi/1/edit?js,console,output'
+      }
+    },
+    {
+      name: `Map and flatten only odd numbers to the sequence 'ax', 'bx', 'cx'`,
+      code: `const source = Rx.Observable.of(1, 2, 3, 4, 5, 6, 7, 8, 9);
+             const result = source.mergeMap(
+               x => x % 2 === 1 ? Rx.Observable.of(\`a\${x}\`, \`b\${x}\`, \`c\${x}\`) :
+                                  Rx.Observable.empty()
+             );
+             const subscription = result.subscribe({
+               next: (x) => console.log(x), // logs result values
+               complete: () => console.log('complete'), // logs 'complete'
+             });`,
+      externalLink: {
+        platform: 'JSBin',
+        url: 'http://jsbin.com/qazabojiri/edit?js,console,output'
+      }
+    }
+  ],
+  relatedOperators: ['create', 'of', 'throw']
 };