Add changelog

Author: alextwoods

.changes/next-release/feature-AWSSignin-b6d69fa.json

@@ -0,0 +1,6 @@
+{
+    "type": "feature",
+    "category": "AWS Signin",
+    "contributor": "",
+    "description": "Add the LoginCredentialsProvider which allows use of AWS credentials vended by AWS Sign-In that correspond to an AWS Console session. AWS Sign-In credentials will be used automatically by the Credential resolution chain when `login_session` is set in the profile."
+}