Add an initial CHANGELOG for firestore (#233)

* Add an initial CHANGELOG for firestore

* Add notes for v4.5.1

* Use Firestore package versions, not global Firebase versions

* Empty commit

Author: wilhuff

packages/firestore/CHANGELOG.md

@@ -0,0 +1,10 @@
+# Unreleased
+- [fixed] Fixed validation of nested arrays to allow indirect nesting
+
+# v0.1.1
+- [fixed] Fixed an issue causing exceptions when trying to use
+  `firebase.firestore.FieldPath.documentId()` in an `orderBy()` or `where()`
+  clause in a query.
+
+# v0.1.0
+- Initial public release.