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/meson.build b/src/meson.build
index ab786c0..5f5c78b 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -56,6 +56,7 @@
   'signal.cpp',
   'str/cat.cpp',
   'str/cexpr.cpp',
+  'str/maps.cpp',
   'util/cexec.cpp',
   'zstring.cpp',
   'zstring_view.cpp',