docs(dialog): address injecting dialog data (#3907)

Author: M-a-c

src/lib/dialog/dialog.md

@@ -29,6 +29,30 @@ Components created via `MdDialog` can _inject_ `MdDialogRef` and use it to close
 in which they are contained. When closing, an optional result value can be provided. This result
 value is forwarded as the result of the `afterClosed` promise. 
 
+### Sharing data with the Dialog component.
+If you want to share data with your dialog, you can use the `data` option to pass information to the dialog component.
+
+```ts
+let dialogRef = dialog.open(YourDialog, {
+  data: 'your data',
+});
+```
+
+To access the data in your dialog component, you have to use the MD_DIALOG_DATA injection token:
+```ts
+import {Component, Inject} from '@angular/core';
+import {MD_DIALOG_DATA} from '@angular/material';
+
+@Component({
+  selector: 'your-dialog',
+  template: 'passed in {{ data }}',
+})
+
+export class YourDialog {
+  constructor(@Inject(MD_DIALOG_DATA) public data: any) { }
+}
+```
+
 ### Dialog content
 Several directives are available to make it easier to structure your dialog content: