net/addr: Support std::format

Change-Id: Ib3e7e7ede426db31322aa114eb750fe298168d9a
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/test/net/addr/ether.cpp b/test/net/addr/ether.cpp
index bff7248..cf23223 100644
--- a/test/net/addr/ether.cpp
+++ b/test/net/addr/ether.cpp
@@ -2,6 +2,8 @@
 
 #include <stdplus/net/addr/ether.hpp>
 
+#include <format>
+
 #include <gtest/gtest.h>
 
 namespace stdplus
@@ -44,6 +46,9 @@
     EXPECT_EQ(
         "a 01:02:03:04:05:67 b",
         fmt::format("a {} b", EtherAddr{0x01, 0x02, 0x03, 0x04, 0x05, 0x67}));
+    EXPECT_EQ(
+        "a 01:02:03:04:05:67 b",
+        std::format("a {} b", EtherAddr{0x01, 0x02, 0x03, 0x04, 0x05, 0x67}));
 }
 
 TEST(FromStr, EtherAddr)