Add WebP tests

Author: kean

Tests/ImageDecoderTests.swift

@@ -133,6 +133,18 @@ class ImageDecoderTests: XCTestCase {
         XCTAssertNotNil(container)
         XCTAssertNil(container?.data)
     }
+
+    func testDecodeBaselineWebP() {
+        let data = Test.data(name: "baseline", extension: "webp")
+        let container = ImageDecoders.Default().decode(data)
+        if #available(OSX 15, iOS 14.0, watchOS 7.0, tvOS 14.0, *) {
+            XCTAssertNotNil(container)
+            XCTAssertNil(container?.data)
+        } else {
+            XCTAssertNil(container)
+            XCTAssertNil(container?.data)
+        }
+    }
 }
 
 class ImageTypeTests: XCTestCase {