Fix conflict: explicit tests and exclude pattern

Author: 197g

Cargo.toml

@@ -8,7 +8,7 @@ repository = "https://github.com/image-rs/jpeg-decoder"
 readme = "README.md"
 keywords = ["jpeg", "jpg", "decoder", "image"]
 license = "MIT / Apache-2.0"
-exclude = ["tests/*"]
+exclude = ["/tests/*", "!/tests/*.rs"]
 edition = "2018"
 
 [dependencies]