docs(cb-dependency-injection): Fix typos

closes #1421

Author: apai4

public/docs/ts/latest/cookbook/dependency-injection.jade

@@ -178,7 +178,7 @@ figure.image-display
 
   Accordingly, dependencies provided in the root `AppComponent` can be injected into *any* component *anywhere* in the application.
 
-  That isn't always desireable. 
+  That isn't always desirable. 
   Sometimes we want to restrict service availability to a particular region of the application.
 
   We can limit the scope of an injected service to a *branch* of the application hierarchy
@@ -277,7 +277,7 @@ a(id="qualify-dependency-lookup")
   placing it in the `<ng-content>` slot of the `HeroBioComponent` template:
 +makeExample('cb-dependency-injection/ts/app/hero-bio.component.ts','template','app/hero-bio.component.ts (template)')(format='.')
 :marked
-  It looks like this, with the heroe's telephone number from `HeroContactComponent` projected above the hero description:
+  It looks like this, with the hero's telephone number from `HeroContactComponent` projected above the hero description:
 figure.image-display
   img(src="/resources/images/cookbooks/dependency-injection/hero-bio-and-content.png" alt="bio and contact")    
 :marked
@@ -308,7 +308,7 @@ figure.image-display
 :marked
   If we comment out the `@Host()` decorator, Angular now walks up the injector ancestor tree 
   until it finds the logger at the `AppComponent` level. The logger logic kicks in and the hero display updates
-  with the gratuituous "!!!", indicating that the logger was found.
+  with the gratuitous "!!!", indicating that the logger was found.
 figure.image-display
   img(src="/resources/images/cookbooks/dependency-injection/hero-bio-contact-no-host.png" alt="Without @Host") 
 :marked
@@ -367,7 +367,7 @@ figure.image-display
 
   Where did the injector get that value?
   It may already have that value in its internal container. 
-  It it doesn't, it may be able to make one with the help of a ***provider***.
+  If it doesn't, it may be able to make one with the help of a ***provider***.
   A *provider* is a recipe for delivering a service associated with a *token*.
 .l-sub-section
   :marked