docs(changelog): include changelog for release 3.4.4

Merged from the 3.4.x branch.

Author: darrachequesne

CHANGELOG.md

@@ -1,3 +1,7 @@
+## [3.4.4](https://github.com/socketio/engine.io-client/compare/3.4.3...3.4.4) (2020-09-30)
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+
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 # [4.0.0](https://github.com/socketio/engine.io-client/compare/v4.0.0-alpha.1...4.0.0) (2020-09-10)
 
 More details about this release in the blog post: https://socket.io/blog/engine-io-4-release/