str/maps: Add commonly used cheaper string map

These maps allow for the use of string_views to find elements so we
don't need to construct std::strings for lookups.

Change-Id: I92040b920bf8e231346bebfe9afa59f1a37b8af5
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/src/str/maps.cpp b/src/str/maps.cpp
new file mode 100644
index 0000000..ed8d63f
--- /dev/null
+++ b/src/str/maps.cpp
@@ -0,0 +1 @@
+#include <stdplus/str/maps.hpp>