Add 1.0.0 release notes to CHANGELOG.md

Summary:
@public

Summary of all changes since 0.9.0. A derived version of this will be featured as the release description (including mentions of contributers)

Reviewed By: cuva

Differential Revision: D13700910

fbshipit-source-id: 9f573f3f1d07fe84ea517bd90474b656fb5dfee6

CHANGELOG.md

@@ -1,3 +1,13 @@
+# 1.0.0 (January 16, 2018)
+
+ - Spectrum can now write interlaced PNG files
+ - Spectrum now supports consuming JPEG images with 4:1:1 and 4:4:0 chroma subsampling (see GitHub issue 8)
+ - Spectrum will default to 4:2:0 chroma subsampling for iOS bitmaps
+ - Spectrum builds with proper SIMD support for mozjpeg on Android ARMv7
+ - Fixed Spectrum build on case-sensitive file systems
+ - Improved documentation
+ - Various fixes and improvements
+
 # 0.9.0 (November 20, 2018)
 
  - Initial release