docs: add changelog for the 4.4.7 release

Author: IgorMinar

CHANGELOG.md

@@ -1,3 +1,13 @@
+<a name="4.4.7"></a>
+## [4.4.7](https://github.com/angular/angular/compare/4.4.6...4.4.7) (2018-04-16)
+
+
+### Bug Fixes
+
+* **core:** use appropriate inert document strategy for Firefox & Safari ([#22077](https://github.com/angular/angular/issues/22077)) ([2c5cf19](https://github.com/angular/angular/commit/2c5cf19))
+
+
+
 <a name="4.4.6"></a>
 ## [4.4.6](https://github.com/angular/angular/compare/4.4.5...4.4.6) (2017-10-18)