message: Improve README for LDBC SNB
diff: DuckDB implementation of the queries from the [LDBC Social Network Benchmark](https://arxiv.org/abs/2001.02299).
  -Download the data:
  +Download the data, initialize the schema, and load the data.
  ```bash
  python download-benchmark-data.py
  -```
  -
  -Initialize the schema:
  -
  -```bash
  cat schema.sql | duckdb ldbc.duckdb
  -```
  -
  -Load the data:
  -
  -```bash
  sed "s|PATHVAR|`pwd`/sf0.1|" snb-load.sql | duckdb ldbc.duckdb
  ```
  