HackStudio: View unstaged diffs in files with DiffViewer

Author: https://github.com/itamar8910
Commit: d1eedd0e9f
Pull-request: https://github.com/SerenityOS/serenity/pull/3470
Reviewed-by: https://github.com/alimpfard
Reviewed-by: https://github.com/awesomekling
Reviewed-by: https://github.com/devsh0

DevTools/HackStudio/CMakeLists.txt

@@ -1,5 +1,6 @@
 set(SOURCES
     CursorTool.cpp
+    Git/DiffViewer.cpp
     Git/GitWidget.cpp
     Git/GitFilesModel.cpp
     Git/GitRepo.cpp
@@ -29,4 +30,4 @@ set(SOURCES
 )
 
 serenity_bin(HackStudio)
-target_link_libraries(HackStudio LibWeb LibMarkdown LibGUI LibGfx LibCore LibVT LibDebug LibX86)
+target_link_libraries(HackStudio LibWeb LibMarkdown LibGUI LibGfx LibCore LibVT LibDebug LibX86 LibDiff)