[NFC] github: Add code owners for AST

Author: AnthonyLatsis

.github/CODEOWNERS

@@ -19,7 +19,6 @@ lib/ASTGen @zoecarver @CodaFi
 
 # Dependency scanning
 include/swift/DependencyScan                 @artemcm
-lib/AST/ModuleLoader.cpp                     @artemcm
 lib/DependencyScan                           @artemcm
 lib/Frontend/ModuleInterfaceLoader.cpp       @artemcm
 lib/Serialization/SerializedModuleLoader.cpp @artemcm
@@ -54,3 +53,22 @@ cmake/**/*Windows*    @compnerd
 lib/Basic/Windows     @compnerd
 stdlib/public/Windows @compnerd
 utils/*windows*       @compnerd
+
+# AST
+/include/swift/AST/               @hborla @slavapestov @xedin
+/include/swift/AST/*Conformance*  @slavapestov
+/include/swift/AST/Evaluator*     @CodaFi @slavapestov
+/include/swift/AST/*Generic*      @hborla @slavapestov
+/include/swift/AST/*Protocol*     @hborla @slavapestov
+/include/swift/AST/*Requirement*  @hborla @slavapestov
+/include/swift/AST/*Substitution* @slavapestov
+/lib/AST/                         @hborla @slavapestov @xedin
+/lib/AST/*Conformance*            @slavapestov
+/lib/AST/Evaluator*               @CodaFi @slavapestov
+/lib/AST/*Generic*                @hborla @slavapestov
+/lib/AST/ModuleLoader.cpp         @artemcm
+/lib/AST/*Requirement*            @hborla @slavapestov
+/lib/AST/RequirementMachine/      @slavapestov
+/lib/AST/*Substitution            @slavapestov
+/unittests/AST/                   @hborla @slavapestov @xedin
+/unittests/AST/*Evaluator*        @CodaFi @slavapestov