docs(readme): Fix links to crates (#1020)

Author: epage

README.md

@@ -2,6 +2,6 @@ This repo contains:
 - [`toml` crate](./crates/toml) for serde support
 - [`toml_edit` crate](./crates/toml_edit) for format-preserving editing of TOML
 - [`toml_datetime` crate](./crates/toml_datetime) for a common type definition between `toml` and `toml_edit`
-- [`serde_spanned` crate](./crates/serde-spanned) for capturing spans when deserializing keys and values
-- [`toml_parser` crate](./crates/toml): a low-level format-preserving TOML lexer and parser
-- [`toml_writer` crate](./crates/toml): a low-level interface for writing out TOML
+- [`serde_spanned` crate](./crates/serde_spanned) for capturing spans when deserializing keys and values
+- [`toml_parser` crate](./crates/toml_parser): a low-level format-preserving TOML lexer and parser
+- [`toml_writer` crate](./crates/toml_writer): a low-level interface for writing out TOML