fix: use relative readme

Author: LeoBorai

src/http-server/Cargo.toml

@@ -8,7 +8,7 @@ repository = "https://github.com/http-server-rs/http-server"
 categories = ["web-programming", "web-programming::http-server"]
 keywords = ["configurable", "http", "server", "serve", "static"]
 license = "MIT OR Apache-2.0"
-readme = "README.md"
+readme = "../../README.md"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html