message: Update README's claim on performance.
diff: @@ -31,12 +31,16 @@ Tantivy is, in fact, strongly inspired by Lucene's design.
  # Benchmark
  -Tantivy is typically faster than Lucene, but the results depend on
  -the nature of the queries in your workload.
  -
  The following [benchmark](https://tantivy-search.github.io/bench/) break downs
  performance for different type of queries / collection.
  +
  +In general, Tantivy tends to be
  +- slower than Lucene 8 on union with a Top-K due to Block-WAND optimization.
  +- faster than Lucene on intersection and phrase queries.
  +
  +Your mileage WILL vary depending on the nature of queries and their load.
  +
  # Features
  - Full-text search
  