Add some excludes

Cargo.toml

@@ -14,6 +14,10 @@ categories = ["cryptography"]
 documentation = "https://docs.rs/ristretto255-dh"
 keywords = ["cryptography", "crypto", "ristretto", "diffie-hellman", "key-exchange"]
 description = "Diffie-Hellman key exchange using the Ristretto255 group."
+exclude = [
+    ".gitignore",
+    ".github/*",
+]
 
 [dependencies]
 curve25519-dalek = { version = "2.0.0", features = ["serde"] }