Fix spelling errors

Great spelling and grammar are important parts of a quality product
as they can be indicators to the level of attention to detail used
for that product.

Small spelling mistakes can go unnoticed but can negatively impact
the opinion of the user even though the underlying product itself
may be excellent.

Author: willem-h

README.md

@@ -45,7 +45,7 @@ FirebaseUI includes the following flows:
 1. Interaction with Identity Providers such as Google and Facebook
 2. Sign-up and sign-in with email accounts
 3. Password reset
-4. Prevention of account duplication (activated when *"One account per email adress"* setting is
+4. Prevention of account duplication (activated when *"One account per email address"* setting is
 enabled in the [Firebase console](https://console.firebase.google.com). This setting is enabled by
 default.)
 5. [Account Chooser](https://www.accountchooser.com/learnmore.html?lang=en) for remembering emails
@@ -294,7 +294,7 @@ widget is not affected by it so you can display everything you want around the w
 
 ### FirebaseUI widget modes
 
-Upon initilization, FirebaseUI will look for the `mode` parameter in the URL. Depending on the value
+Upon initialization, FirebaseUI will look for the `mode` parameter in the URL. Depending on the value
 of this parameter, it will trigger a specific mode. When no `mode` parameter is found, it will
 default to the sign-in mode.