[CI] Add JDK 18-ea to the build matrix.

Author: vyazelenko

.github/workflows/ci.yml

@@ -19,7 +19,7 @@ jobs:
  strategy:
  fail-fast: false
  matrix:
- java: [ '8', '11', '17' ]
+ java: [ '8', '11', '17', '18-ea' ]
  os: [ 'ubuntu-20.04', 'windows-latest' ]
  steps:
  - name: Checkout code