Add More Details to README

extensions/Bitwarden.Server.Sdk/src/README.md

@@ -6,3 +6,13 @@ on your web application and configuring MSBuild properties to configure the feat
 want.
 
 ## Feature Flags
+
+Feature flag support can be added by adding `<BitIncludeFeatures>true</BitIncludeFeatures>` to
+your `csproj` file. The following API's become available:
+
+- `IFeatureService` for getting values of features.
+- `RequireFeatureAttribute` for requiring a feature is enabled on controllers and controller actions.
+- `IEndpointConventionBuilder.RequireFeature()` for requiring a feature is enabled on minimal API's.
+- `IApplicationBuilder.UseFeatureFlagChecks()` for adding the middleware to do the above checks.
+- `IServiceCollection.AddKnownFeatureFlags()` for adding flags that will show up in `IFeatureService.GetAll()`
+- `IServiceCollection.AddFeatureFlagValues()` for adding values for feature flags.