Fix typo (angular#1429)

LuxDie · davideast · commit 72f7d9649e11 · 2018-01-17T13:55:30.000-07:00
diff --git a/docs/firestore/collections.md b/docs/firestore/collections.md
@@ -37,7 +37,7 @@ export class AppComponent {
 }
 ```
 
-The `AngularFirestoreCollection` is service you use to create streams of the collection and perform data operations on the underyling collection.
+The `AngularFirestoreCollection` is a service you use to create streams of the collection and perform data operations on the underyling collection.
 
 ### The `DocumentChangeAction` type
 

Original file line number	Diff line number	Diff line change
`@@ -37,7 +37,7 @@ export class AppComponent {`
`37`	`37`	`}`
`38`	`38`	```
`39`	`39`
`40`		-The `AngularFirestoreCollection` is service you use to create streams of the collection and perform data operations on the underyling collection.
	`40`	+The `AngularFirestoreCollection` is a service you use to create streams of the collection and perform data operations on the underyling collection.
`41`	`41`
`42`	`42`	### The `DocumentChangeAction` type
`43`	`43`