Add module description for ContainerizationEXT4 (#14)

Signed-off-by: Eric Ernst <eric_ernst@apple.com>

Package.swift

@@ -110,6 +110,10 @@ let package = Package(
                 .target(name: "ContainerizationArchive", condition: .when(platforms: [.macOS])),
                 .product(name: "SystemPackage", package: "swift-system"),
                 "ContainerizationOS",
+            ],
+            path: "Sources/ContainerizationEXT4",
+            exclude: [
+                "README.md"
             ]
         ),
         .testTarget(

Sources/ContainerizationEXT4/Documentation.docc/ext4.md

@@ -0,0 +1,4 @@
+# ``ContainerizationEXT4``
+
+`ContainerizationEXT4` provides functionality to read the superblock of an existing ext4 block device and format a new block device with
+the ext4 file system.

Sources/ContainerizationEXT4/README.md

@@ -0,0 +1,4 @@
+# ``ContainerizationEXT4``
+
+`ContainerizationEXT4` provides functionality to read the superblock of an existing ext4 block device and format a new block device with
+the ext4 file system.