Add workspaces to PackageJson type

source/package-json.d.ts

@@ -257,8 +257,26 @@ declare namespace PackageJson {
 		typings?: string;
 	}
 
+	export interface Workspaces {
+		/**
+		The packages blob to use for workspaces.
+		*/
+		packages: string[];
+		/**
+		A list of glob patterns for packages that should not be hoisted.
+		*/
+		nohoist: string[];
+	}
+
 	export interface YarnConfiguration {
 		/**
+    Used to configure yarn (and other) workspaces.
+
+    Please note private should be set to true to use workspaces
+    */
+    workspaces?: string[] | Workspaces;
+
+		/**
 		If your package only allows one version of a given dependency, and you’d like to enforce the same behavior as `yarn install --flat` on the command line, set this to `true`.
 
 		Note that if your `package.json` contains `"flat": true` and other packages depend on yours (e.g. you are building a library rather than an application), those other packages will also need `"flat": true` in their `package.json` or be installed with `yarn install --flat` on the command-line.

test-d/package-json.ts

@@ -35,6 +35,7 @@ expectType<PackageJson.Dependency | undefined>(packageJson.peerDependencies);
 expectType<string[] | undefined>(packageJson.bundleDependencies);
 expectType<string[] | undefined>(packageJson.bundledDependencies);
 expectType<PackageJson.Dependency | undefined>(packageJson.resolutions);
+expectType<PackageJson.Workspaces | string[] | undefined>(packageJson.workspaces);
 expectType<{[engineName: string]: string} | undefined>(packageJson.engines);
 expectType<boolean | undefined>(packageJson.engineStrict);
 expectType<