Minor: Fix Self referential links in readme (#9119)

* Minor: Fix Self referential links in readme

* prettier

* Improve readme

Author: alamb

datafusion/core/README.md

@@ -19,8 +19,13 @@
 
 # DataFusion Core
 
-[DataFusion][df] is an extensible query execution framework, written in Rust, that uses Apache Arrow as its in-memory format.
+DataFusion is an extensible query execution framework, written in Rust,
+that uses Apache Arrow as its in-memory format.
 
-This crate contains the main entrypoints and high level DataFusion APIs such as SessionContext, and DataFrame and ListingTable.
+This crate contains the main entry points and high level DataFusion APIs such as
+`SessionContext`, `DataFrame` and `ListingTable`.
 
-[df]: https://crates.io/crates/datafusion
+For more information, please see:
+
+- [DataFusion Website](https://arrow.apache.org/datafusion)
+- [DataFusion API Docs](https://docs.rs/datafusion/latest/datafusion/)