Update README.md (#47)

Add link to https://parquet.apache.org

README.md

@@ -4,7 +4,7 @@
 
 [![CI lints and tests](https://github.com/CrunchyData/pg_parquet/actions/workflows/ci.yml/badge.svg)](https://github.com/CrunchyData/pg_parquet/actions/workflows/ci.yml)
 
-`pg_parquet` is a PostgreSQL extension that allows you to read and write Parquet files, which are located in `S3` or `file system`, from PostgreSQL via `COPY TO/FROM` commands. It depends on [Apache Arrow](https://arrow.apache.org/rust/arrow/) project to read and write Parquet files and [pgrx](https://github.com/pgcentralfoundation/pgrx) project to extend PostgreSQL's `COPY` command.
+`pg_parquet` is a PostgreSQL extension that allows you to read and write [Parquet files](https://parquet.apache.org), which are located in `S3` or `file system`, from PostgreSQL via `COPY TO/FROM` commands. It depends on [Apache Arrow](https://arrow.apache.org/rust/arrow/) project to read and write Parquet files and [pgrx](https://github.com/pgcentralfoundation/pgrx) project to extend PostgreSQL's `COPY` command.
 
 ```sql
 -- Copy a query result into Parquet in S3