Fix GPG signing order and revert to snapshot

Move maven-gpg-plugin after javadoc and source plugins in the release
profile so GPG signs all artifacts including javadoc and sources JARs.
Revert version to 999-SNAPSHOT after the 0.0.1 release.

Author: andreaTP

pom.xml

@@ -4,7 +4,7 @@
 
   <groupId>io.roastedroot</groupId>
   <artifactId>oras-java</artifactId>
-  <version>0.0.1</version>
+  <version>999-SNAPSHOT</version>
   <packaging>jar</packaging>
   <name>${project.groupId}:${project.artifactId}</name>
   <description>ORAS Java SDK - Java 11 compatible fork</description>
@@ -672,15 +672,15 @@
         <plugins>
           <plugin>
             <groupId>org.apache.maven.plugins</groupId>
-            <artifactId>maven-gpg-plugin</artifactId>
+            <artifactId>maven-javadoc-plugin</artifactId>
           </plugin>
           <plugin>
             <groupId>org.apache.maven.plugins</groupId>
-            <artifactId>maven-javadoc-plugin</artifactId>
+            <artifactId>maven-source-plugin</artifactId>
           </plugin>
           <plugin>
             <groupId>org.apache.maven.plugins</groupId>
-            <artifactId>maven-source-plugin</artifactId>
+            <artifactId>maven-gpg-plugin</artifactId>
           </plugin>
           <plugin>
             <groupId>org.sonatype.central</groupId>