Rename changelog and fix Markdown formatting (#36)

Author: andrewheard

CHANGELOG.md

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+# 11.5.0-beta
+- [added] Support for Swift 6 strict concurrency.
+- [added] Logging within SDKs.
+- [changed] SDK will throw errors if partial GraphQL errors are detected during operation execution.
+
+# 11.3.0-beta
+- [added] Initial public preview (pre-announced) release of the SDK. For more information visit
+  [Firebase Data Connect](https://firebase.google.com/products/data-connect).