CODEOWNERS: Add some specific people to files (#58357)

Author: LilithHafner

.github/CODEOWNERS

@@ -4,3 +4,10 @@ CODEOWNERS @JuliaLang/github-actions
 
 /.github/workflows/rerun_failed.yml @DilumAluthge
 /.github/workflows/statuses.yml @DilumAluthge
+/base/special/ @oscardssmith
+/base/sort.jl @LilithHafner
+/test/sorting.jl @LilithHafner
+/stdlib/*_jll @giordano
+/base/binaryplatforms.jl @giordano
+/src/julia_gcext.h @fingolfin
+/test/gcext/gcext.c @fingolfin