[libc++] [P1612] Add missing feature-test macro __cpp_lib_endian.

Thanks to Marek Kurdej for the patch.

Differential Revision: https://reviews.llvm.org/D70221

Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 8b77a3a0f4ef8c2cda3a0437fe54e2c2ecef1b17
diff --git a/docs/FeatureTestMacroTable.rst b/docs/FeatureTestMacroTable.rst
index 2200a99..3dd00fa 100644
--- a/docs/FeatureTestMacroTable.rst
+++ b/docs/FeatureTestMacroTable.rst
@@ -20,7 +20,7 @@
 .. table:: Current Status
      :name: feature-status-table
      :widths: auto
-     
+
     ================================================= =================
     Macro Name                                        Value            
     ================================================= =================
@@ -184,6 +184,8 @@
     ------------------------------------------------- -----------------
     ``__cpp_lib_destroying_delete``                   ``201806L``      
     ------------------------------------------------- -----------------
+    ``__cpp_lib_endian``                              ``201907L``      
+    ------------------------------------------------- -----------------
     ``__cpp_lib_erase_if``                            ``201811L``      
     ------------------------------------------------- -----------------
     ``__cpp_lib_generic_unordered_lookup``            *unimplemented*