Update README.md

Author: bitfaster

README.md

@@ -1,4 +1,21 @@
 # BitFaster.Caching.DependencyInjection
 Extension methods for setting up caches using Microsoft.Extensions.DependencyInjection.
 
-Currently work in progress.
+# ConcurrentLru
+
+```cs
+services.AddLru<int, int>(builder =>
+    builder
+        .WithCapacity(666)
+        .Build());
+```
+
+
+# ConcurrentLfu
+
+```cs
+services.AddLfu<int, int>(builder =>
+    builder
+        .WithCapacity(666)
+        .Build());
+```