Added the Swift DocC Plugin dependency to the Package file.

Package.resolved

@@ -1,5 +1,23 @@
 {
   "pins" : [
+    {
+      "identity" : "swift-docc-plugin",
+      "kind" : "remoteSourceControl",
+      "location" : "https://github.com/apple/swift-docc-plugin",
+      "state" : {
+        "revision" : "9b1258905c21fc1b97bf03d1b4ca12c4ec4e5fda",
+        "version" : "1.2.0"
+      }
+    },
+    {
+      "identity" : "swift-docc-symbolkit",
+      "kind" : "remoteSourceControl",
+      "location" : "https://github.com/apple/swift-docc-symbolkit",
+      "state" : {
+        "revision" : "b45d1f2ed151d057b54504d653e0da5552844e34",
+        "version" : "1.0.0"
+      }
+    },
     {
       "identity" : "swift-libs",
       "kind" : "remoteSourceControl",

Package.swift

@@ -19,7 +19,8 @@ let package = Package(
         ),
     ],
     dependencies: [
-        .package(url: "https://github.com/rock-n-code/swift-libs.git", from: "0.1.0")
+        .package(url: "https://github.com/rock-n-code/swift-libs.git", from: "0.1.0"),
+        .package(url: "https://github.com/apple/swift-docc-plugin", from: "1.1.0"),
     ],
     targets: [
         .target(