docs: link the website from the crates and the READMEs

The site went up but nothing pointed at it. `homepage` in the workspace
package metadata gives both crates.io pages a link, and each README opens with
one, so someone landing on the crate or the repo can find the install guide
and the config reference.

soulseek-rs-lib/Cargo.toml

@@ -5,6 +5,7 @@ authors.workspace = true
 edition.workspace = true
 license.workspace = true
 repository.workspace = true
+homepage.workspace = true
 description = "Library for Soulseek protocol implementation in Rust"
 keywords = ["soulseek", "p2p", "protocol", "file-sharing"]
 categories = ["network-programming"]