[clang-format] Releasenotes for rL319024 : Add option to group multiple...

[clang-format] Releasenotes for rL319024 : Add option to group multiple #include blocks when sorting includes

Summary:
This change adds missing releasenotes for commit rL319024
https://reviews.llvm.org/rL319024

Patch by Krzysztof Kapusta

Reviewers: sylvestre.ledru

Reviewed By: sylvestre.ledru

Differential Revision: https://reviews.llvm.org/D40827

llvm-svn: 319748