Add pybind11/compat/README.txt to wheels.

Author: rwgk

tests/extra_python_package/test_files.py

@@ -51,6 +51,7 @@
 }
 
 compat_headers = {
+    "include/pybind11/compat/README.txt",
     "include/pybind11/compat/pybind11_conduit_v1.h",
     "include/pybind11/compat/pybind11_platform_abi_id.h",
     "include/pybind11/compat/wrap_include_python_h.h",

tools/setup_global.py.in

@@ -26,7 +26,8 @@ class InstallHeadersNested(install_headers):
 
 
 main_headers = glob.glob("pybind11/include/pybind11/*.h")
-compat_headers = glob.glob("pybind11/include/pybind11/compat/*.h")
+compat_headers = sum([glob.glob(f"pybind11/include/pybind11/compat/*.{ext}")
+                      for ext in ("h", "txt")], [])
 detail_headers = glob.glob("pybind11/include/pybind11/detail/*.h")
 eigen_headers = glob.glob("pybind11/include/pybind11/eigen/*.h")
 stl_headers = glob.glob("pybind11/include/pybind11/stl/*.h")

tools/setup_main.py.in

@@ -24,7 +24,7 @@ setup(
     package_data={
         "pybind11": ["py.typed"],
         "pybind11.include.pybind11": ["*.h"],
-        "pybind11.include.pybind11.compat": ["*.h"],
+        "pybind11.include.pybind11.compat": ["*.h", "*.txt"],
         "pybind11.include.pybind11.detail": ["*.h"],
         "pybind11.include.pybind11.eigen": ["*.h"],
         "pybind11.include.pybind11.stl": ["*.h"],