[libc] add headers.txt for windows (#118675)

Link:
#117220 (comment)

---------

Co-authored-by: Michael Jones <[email protected]>

Author: nickdesaulniers

libc/config/windows/headers.txt

@@ -0,0 +1,9 @@
+set(TARGET_PUBLIC_HEADERS
+    libc.include.ctype
+    libc.include.string
+    libc.include.inttypes
+    libc.include.stdlib
+    libc.include.errno
+    libc.include.fenv
+    libc.include.math
+)