docs: updated changelog for 1.1.0

Author: dees040

docs/changes/1.1.0.md

@@ -34,6 +34,7 @@
 - PowerPoint2007 Writer : Fixed broken animation for first shape - [@shannan1989](https://github.com/shannan1989) in [#783](https://github.com/PHPOffice/PHPPresentation/pull/783)
 - Samples : Allow to run without composer - [@pal-software](https://github.com/pal-software) in [#784](https://github.com/PHPOffice/PHPPresentation/pull/784)
 - PowerPoint2007 Writer: Extract relations from nested ShapeContainerInterface objects - [@DennisBirkholz](https://github.com/DennisBirkholz) in [#785](https://github.com/PHPOffice/PHPPresentation/pull/785)
+- General : Fixed copying bug when presentation had multiple slides [@dees040](https://github.com/dees040) in [#786](https://github.com/PHPOffice/PHPPresentation/pull/786)
 
 ## Miscellaneous