Remove gitmodule for Catch2, replaced it with header file

CMakeLists.txt

@@ -2,12 +2,12 @@ cmake_minimum_required(VERSION 3.13)
 project(PorygonLang)
 
 set(CMAKE_CXX_STANDARD 17)
-add_subdirectory(extern/Catch2)
+#add_subdirectory(extern)
+include_directories(extern)
 
 add_library(PorygonLang src/main.cpp src/main.h++ src/Parser/Lexer.cpp src/Parser/Lexer.hpp src/Parser/TokenKind.hpp src/Parser/Token.hpp)
 add_executable(PorygonLangTests src/main.cpp src/main.h++ src/Parser/Lexer.cpp src/Parser/Lexer.hpp src/Parser/TokenKind.hpp src/Parser/Token.hpp src/Parser/LexerTests.cpp)
 
-target_link_libraries(PorygonLangTests Catch2::Catch2)
 target_compile_definitions(PorygonLangTests PRIVATE TESTS_BUILD)