docs(changelog): add contributors section (#11576)

Author: Splaktar

CHANGELOG.md

@@ -7,7 +7,13 @@
 * **select:** multiple with initial value causes label to overlap with value ([#11572](https://github.com/angular/material/issues/11572)) ([a4507d6](https://github.com/angular/material/commit/a4507d6)), closes [#11571](https://github.com/angular/material/issues/11571) [#11571](https://github.com/angular/material/issues/11571)
 * **tabs:** md-center-tabs causes tabs to not render ([#11567](https://github.com/angular/material/issues/11567)) ([a49043d](https://github.com/angular/material/commit/a49043d)), closes [#11566](https://github.com/angular/material/issues/11566) [#11432](https://github.com/angular/material/issues/11432)
 
+#### Contributors
+
+Thank you to the contributors who helped with the v1.1.12 release over the holiday break:
 
+[<img alt="Splaktar" src="https://avatars1.githubusercontent.com/u/3506071?v=4&s=117" width="117">](https://github.com/Splaktar) |[<img alt="codymikol" src="https://avatars1.githubusercontent.com/u/13606342?v=4&s=117" width="117">](https://github.com/codymikol) |[<img alt="mmalerba" src="https://avatars1.githubusercontent.com/u/14793288?v=4&s=117" width="117">](https://github.com/mmalerba) |
+:---: |:---: |:---: |
+[Splaktar](https://github.com/Splaktar) |[codymikol](https://github.com/codymikol) |[mmalerba](https://github.com/mmalerba) |
 
 <a name="1.1.11"></a>
 ## [1.1.11](https://github.com/angular/material/compare/v1.1.10...v1.1.11) (2018-12-20)