Add v3.4.5 to CHANGELOG

[ci skip]

(cherry picked from commit 82b0b2d)

CHANGELOG.md

@@ -19,6 +19,10 @@
 - [#16877](https://github.com/emberjs/ember.js/pull/16877) [CLEANUP] Allow routes to be named "array" and "object"
 - [#16907](https://github.com/emberjs/ember.js/pull/16907) Upgrade to TypeScript 3.0
 
+### v3.4.5 (October 4, 2018)
+
+- [#17029](https://github.com/emberjs/ember.js/pull/17029) [BUGFIX] Update backburner.js to 2.3.1.
+
 ### v3.4.4 (September 27, 2018)
 
 - [#17013](https://github.com/emberjs/ember.js/pull/17013) [BUGFIX] Fix rendering of empty content with `{{{...}}}` or `{{...}}` with `htmlSafe('')` in IE11