Include new Early-Access builds of `jextract`

Include new Early-Access builds of `jextract` when listing available JDKs from https://jdk.java.net/jextract/

This allows installing an EA image with `jextract` via:
```
steps:
  - name: 'Set up Early-Access build of jextract from jdk.java.net'
    uses: oracle-actions/setup-java@v1
    with:
      website: jdk.java.net
      release: jextract
```