Update the CMake files to version 4

Patch submitted upstream, along with other improvements:
https://github.com/github/cmark-gfm/pull/390

--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.0)
+cmake_minimum_required(VERSION 4.0)
 project(cmark-gfm)
 
 set(PROJECT_VERSION_MAJOR 0)
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -4,9 +4,9 @@
 # To require the spec tests, compile with -DSPEC_TESTS=1
 
 if (SPEC_TESTS)
-  find_package(PythonInterp 3 REQUIRED)
+  find_package(Python 3 COMPONENTS Interpreter REQUIRED)
 else(SPEC_TESTS)
-  find_package(PythonInterp 3)
+  find_package(Python 3 COMPONENTS Interpreter)
 endif(SPEC_TESTS)
 
 if (CMARK_SHARED OR CMARK_STATIC)
@@ -24,48 +24,48 @@
   set(ROUNDTRIP "${CMAKE_CURRENT_SOURCE_DIR}/roundtrip.sh")
 endif(WIN32)
 
-IF (PYTHONINTERP_FOUND)
+IF (Python_Interpreter_FOUND)
 
   add_test(html_normalization
-    ${PYTHON_EXECUTABLE} "-m" "doctest"
+    ${Python_EXECUTABLE} "-m" "doctest"
     "${CMAKE_CURRENT_SOURCE_DIR}/normalize.py"
     )
 
   if (CMARK_SHARED)
     add_test(spectest_library
-      ${PYTHON_EXECUTABLE} "${CMAKE_CURRENT_SOURCE_DIR}/spec_tests.py" "--no-normalize" "--spec"
+       ${Python_EXECUTABLE} "${CMAKE_CURRENT_SOURCE_DIR}/spec_tests.py" "--no-normalize" "--spec"
       "${CMAKE_CURRENT_SOURCE_DIR}/spec.txt" "--library-dir" "${CMAKE_CURRENT_BINARY_DIR}/../src"
       )
 
     add_test(pathological_tests_library
-      ${PYTHON_EXECUTABLE} "${CMAKE_CURRENT_SOURCE_DIR}/pathological_tests.py"
+      ${Python_EXECUTABLE} "${CMAKE_CURRENT_SOURCE_DIR}/pathological_tests.py"
       "--library-dir" "${CMAKE_CURRENT_BINARY_DIR}/../src"
       )
 
     add_test(roundtriptest_library
-      ${PYTHON_EXECUTABLE}
+      ${Python_EXECUTABLE}
       "${CMAKE_CURRENT_SOURCE_DIR}/roundtrip_tests.py"
       "--spec" "${CMAKE_CURRENT_SOURCE_DIR}/spec.txt"
       "--library-dir" "${CMAKE_CURRENT_BINARY_DIR}/../src"
       )
 
     add_test(entity_library
-      ${PYTHON_EXECUTABLE}
+      ${Python_EXECUTABLE}
       "${CMAKE_CURRENT_SOURCE_DIR}/entity_tests.py"
       "--library-dir" "${CMAKE_CURRENT_BINARY_DIR}/../src"
       )
   endif()
 
   add_test(spectest_executable
-    ${PYTHON_EXECUTABLE} "${CMAKE_CURRENT_SOURCE_DIR}/spec_tests.py" "--no-normalize" "--spec" "${CMAKE_CURRENT_SOURCE_DIR}/spec.txt" "--program" "${CMAKE_CURRENT_BINARY_DIR}/../src/cmark-gfm"
+    ${Python_EXECUTABLE} "${CMAKE_CURRENT_SOURCE_DIR}/spec_tests.py" "--no-normalize" "--spec" "${CMAKE_CURRENT_SOURCE_DIR}/spec.txt" "--program" "${CMAKE_CURRENT_BINARY_DIR}/../src/cmark-gfm"
     )
 
   add_test(smartpuncttest_executable
-    ${PYTHON_EXECUTABLE} "${CMAKE_CURRENT_SOURCE_DIR}/spec_tests.py" "--no-normalize" "--spec" "${CMAKE_CURRENT_SOURCE_DIR}/smart_punct.txt" "--program" "${CMAKE_CURRENT_BINARY_DIR}/../src/cmark-gfm --smart"
+    ${Python_EXECUTABLE} "${CMAKE_CURRENT_SOURCE_DIR}/spec_tests.py" "--no-normalize" "--spec" "${CMAKE_CURRENT_SOURCE_DIR}/smart_punct.txt" "--program" "${CMAKE_CURRENT_BINARY_DIR}/../src/cmark-gfm --smart"
     )
 
   add_test(extensions_executable
-    ${PYTHON_EXECUTABLE}
+    ${Python_EXECUTABLE}
     "${CMAKE_CURRENT_SOURCE_DIR}/spec_tests.py"
     "--no-normalize"
     "--spec" "${CMAKE_CURRENT_SOURCE_DIR}/extensions.txt"
@@ -74,7 +74,7 @@
     )
 
   add_test(roundtrip_extensions_executable
-    ${PYTHON_EXECUTABLE}
+    ${Python_EXECUTABLE}
     "${CMAKE_CURRENT_SOURCE_DIR}/roundtrip_tests.py"
     "--spec" "${CMAKE_CURRENT_SOURCE_DIR}/extensions.txt"
     "--program" "${CMAKE_CURRENT_BINARY_DIR}/../src/cmark-gfm"
@@ -82,7 +82,7 @@
     )
 
   add_test(option_table_prefer_style_attributes
-    ${PYTHON_EXECUTABLE}
+    ${Python_EXECUTABLE}
     "${CMAKE_CURRENT_SOURCE_DIR}/roundtrip_tests.py"
     "--spec" "${CMAKE_CURRENT_SOURCE_DIR}/extensions-table-prefer-style-attributes.txt"
     "--program" "${CMAKE_CURRENT_BINARY_DIR}/../src/cmark-gfm --table-prefer-style-attributes"
@@ -90,25 +90,25 @@
     )
 
   add_test(option_full_info_string
-    ${PYTHON_EXECUTABLE}
+    ${Python_EXECUTABLE}
     "${CMAKE_CURRENT_SOURCE_DIR}/roundtrip_tests.py"
     "--spec" "${CMAKE_CURRENT_SOURCE_DIR}/extensions-full-info-string.txt"
     "--program" "${CMAKE_CURRENT_BINARY_DIR}/../src/cmark-gfm --full-info-string"
     )
 
   add_test(regressiontest_executable
-    ${PYTHON_EXECUTABLE}
+    ${Python_EXECUTABLE}
     "${CMAKE_CURRENT_SOURCE_DIR}/spec_tests.py" "--no-normalize" "--spec"
     "${CMAKE_CURRENT_SOURCE_DIR}/regression.txt" "--program"
     "${CMAKE_CURRENT_BINARY_DIR}/../src/cmark-gfm"
     )
 
 
-ELSE(PYTHONINTERP_FOUND)
+ELSE(Python_Interpreter_FOUND)
 
   message("\n*** A python 3 interpreter is required to run the spec tests.\n")
   add_test(skipping_spectests
     echo "Skipping spec tests, because no python 3 interpreter is available.")
 
-ENDIF(PYTHONINTERP_FOUND)
+ENDIF(Python_Interpreter_FOUND)