Add banner like other SDKs have (#2877)

Author: Sushisource

README.md

@@ -1,3 +1,5 @@
+![Temporal Java SDK](https://raw.githubusercontent.com/temporalio/assets/main/files/w/java.png)
+
 # Temporal Java SDK  [![Build status](https://github.com/temporalio/sdk-java/actions/workflows/ci.yml/badge.svg?event=push)](https://github.com/temporalio/sdk-java/actions/workflows/ci.yml) [![Coverage Status](https://coveralls.io/repos/github/temporalio/sdk-java/badge.svg?branch=master)](https://coveralls.io/github/temporalio/sdk-java?branch=master)
 
 [Temporal](https://github.com/temporalio/temporal) is a Workflow-as-Code platform for building and operating
@@ -95,4 +97,4 @@ Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS,
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
-limitations under the License.
+limitations under the License.