Use official Antora Maven Plugin

- Use the latest Antora Maven Plugin
- Switch to package.json (this allows dependabot to update the versions)
- Also works around https://github.com/asciidoctor/asciidoctor.js/issues/1732 by
  by forcing the asciidoctor.js version to previous release

.gitignore

@@ -18,4 +18,3 @@ src/ant/.ant-targets-upload-dist.xml
 node_modules
 node/
 package-lock.json
-package.json

package.json

@@ -0,0 +1,12 @@
+{
+    "//": "Until it is fixed, force asciidoctor/core version https://github.com/asciidoctor/asciidoctor.js/issues/1732",
+    "dependencies": {
+        "antora": "3.2.0-alpha.4",
+        "@asciidoctor/core": "2.2.6",
+        "@antora/atlas-extension": "1.0.0-alpha.2",
+        "@antora/collector-extension": "1.0.0-alpha.3",
+        "@asciidoctor/tabs": "1.0.0-beta.6",
+        "@springio/antora-extensions": "1.11.1",
+        "@springio/asciidoctor-extensions": "1.0.0-alpha.10"
+    }
+}

pom.xml

@@ -22,15 +22,16 @@
     </issueManagement>
 
     <properties>
-        <io.spring.maven.antora-version>0.0.4</io.spring.maven.antora-version>
+        <maven.antora-version>1.0.0-alpha.4</maven.antora-version>
     </properties>
 
     <build>
         <plugins>
+
             <plugin>
-                <groupId>io.spring.maven.antora</groupId>
+                <groupId>org.antora</groupId>
                 <artifactId>antora-maven-plugin</artifactId>
-                <version>${io.spring.maven.antora-version}</version>
+                <version>${maven.antora-version}</version>
                 <extensions>true</extensions>
                 <configuration>
                     <options>
@@ -38,13 +39,6 @@
                         <option>--stacktrace</option>
                         <option>--fetch</option>
                     </options>
-                    <packages>
-                        <package>@antora/atlas-extension@1.0.0-alpha.1</package>
-                        <package>@antora/collector-extension@1.0.0-alpha.3</package>
-                        <package>@asciidoctor/tabs@1.0.0-beta.3</package>
-                        <package>@springio/antora-extensions@1.11.1</package>
-                        <package>@springio/asciidoctor-extensions@1.0.0-alpha.9</package>
-                    </packages>
                 </configuration>
             </plugin>
         </plugins>