Updating docs for itemsToGenerate (apollographql#3200)

Sources/ApolloCodegenLib/ApolloCodegen.swift

@@ -68,11 +68,18 @@ public class ApolloCodegen {
     }
   }
 
+  /// OptionSet used to configure what items should be generated during code generation.
   public struct ItemsToGenerate: OptionSet {
     public var rawValue: Int
 
+    /// Only generate your code (Operations, Fragments, Enums, etc), this option maintains the codegen functionality
+    /// from before this option set was created.
     public static let code = ItemsToGenerate(rawValue: 1 << 0)
+
+    /// Only generate the operation manifest used for persisted queries and automatic persisted queries.
     public static let operationManifest = ItemsToGenerate(rawValue: 1 << 1)
+
+    /// Generate all available items during code generation.
     public static let all: ItemsToGenerate = [
       .code,
       .operationManifest
@@ -91,6 +98,8 @@ public class ApolloCodegen {
   ///     during code generation.
   ///   - rootURL: The root `URL` to resolve relative `URL`s in the configuration's paths against.
   ///     If `nil`, the current working directory of the executing process will be used.
+  ///   - itemsToGenerate: Uses the `ItemsToGenerate` option set to determine what items should be generated during codegen.
+  ///     By default this will use [.code] which maintains how codegen functioned prior to these options being added.
   public static func build(
     with configuration: ApolloCodegenConfiguration,
     withRootURL rootURL: URL? = nil,

docs/source/code-generation/run-codegen-in-swift-code.mdx

@@ -31,14 +31,14 @@ Once you've installed the `ApolloCodegenLib` dependency in your project, you can
 
 - [Installing `ApolloCodegenLib`](#installing-apollocodegenlib)
 - [Usage](#usage)
-  - [Running code generation](#running-code-generation)
-  - [Downloading a schema](#downloading-a-schema)
+	- [Running code generation](#running-code-generation)
+	- [Downloading a schema](#downloading-a-schema)
 
 ### Running code generation
 
-To configure and run code generation using `ApolloCodegenLib`, create an [`ApolloCodegenConfiguration`](https://www.apollographql.com/docs/ios/docc/documentation/apollocodegenlib/apollocodegenconfiguration), then pass it to `ApolloCodegen.build(with configuration:withRootURL:)` function.
+To configure and run code generation using `ApolloCodegenLib`, create an [`ApolloCodegenConfiguration`](https://www.apollographql.com/docs/ios/docc/documentation/apollocodegenlib/apollocodegenconfiguration), then pass it to `ApolloCodegen.build(with configuration:withRootURL:itemsToGenerate:)` function.
 
-By default, the Code Generation Engine will resolve all file paths in your `ApolloCodegenConfiguration` relative to the current working directory. The `rootURL` parameter can be used to provide a local file path URL of the root of the project that you want to run code generation on. This will resolve file paths in your configuration relative to the provided `rootURL`.
+By default, the Code Generation Engine will resolve all file paths in your `ApolloCodegenConfiguration` relative to the current working directory. The `rootURL` parameter can be used to provide a local file path URL of the root of the project that you want to run code generation on. This will resolve file paths in your configuration relative to the provided `rootURL`. The [`itemsToGenerate`](https://www.apollographql.com/docs/ios/docc/documentation/apollocodegenlib/apollocodegen/itemsToGenerate) parameter allows you to customize what items will be generated. If you don't provide options this will default to `[.code]` which will just generate code files in the same way code generation worked prior to this option set being added in version 1.4.0. 
 
 ```swift
 import ApolloCodegenLib