Update ci.yml

Add 19-ea, use released 18
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index e12698c..c5cea7a 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -29,19 +29,19 @@
       fail-fast: false
       matrix:
         os: [ ubuntu-latest ]
-        java: [ 17, 11 ]
+        java: [ 18, 17, 11 ]
         experimental: [ false ]
         include:
           # Only test on macos and windows with a single recent JDK to avoid a
           # combinatorial explosion of test configurations.
           - os: macos-latest
-            java: 17
+            java: 18
             experimental: false
           - os: windows-latest
-            java: 17
+            java: 18
             experimental: false
           - os: ubuntu-latest
-            java: 18-ea
+            java: 19-ea
             experimental: true
     runs-on: ${{ matrix.os }}
     continue-on-error: ${{ matrix.experimental }}