[DOC] Update title and description in README (#94)

### What changes were proposed in this pull request?

Add "Apache" in the title and improve the description.

### Does this PR introduce _any_ user-facing change?

No.

### How was this patch tested?

See https://github.com/kaijchen/incubator-uniffle/tree/readme#apache-uniffle-incubating

Co-authored-by: roryqi <jerqi1242949407@gmail.com>

README.md

@@ -15,10 +15,12 @@
   ~ limitations under the License.
   -->
 
-# What is Uniffle
+# Apache Uniffle (Incubating)
 
-Uniffle is a Remote Shuffle Service, and provides the capability for Apache Spark applications
-to store shuffle data on remote servers.
+Uniffle is a unified remote shuffle service for compute engines.
+It provides the ability to aggregate and store shuffle data on remote servers,
+thus improving the performance and reliability of large jobs.
+Currently it supports [Apache Spark](https://spark.apache.org) and [MapReduce](https://hadoop.apache.org).
 
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