add pg18 support

.github/CODEOWNERS

@@ -1 +1 @@
-*       @ChuckHend @ianstanton @ryw @sjmiller609 @nhudson
+*       @ChuckHend

.github/actions/pgx-init/action.yml

@@ -8,6 +8,11 @@ outputs: {}
 runs:
   using: "composite"
   steps:
+      - name: OS dependencies
+        shell: bash
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y build-essential libreadline-dev zlib1g-dev flex bison libxml2-dev libxslt-dev libssl-dev libxml2-utils xsltproc ccache pkg-config
       - name: Install TOML parser
         shell: bash
         run: |