SPIGOT-4265: Declare org.bukkit module

By: md_5 <git@md-5.net>

paper-api/pom.xml

@@ -110,6 +110,18 @@
                     </dependency>
                 </dependencies>
             </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-jar-plugin</artifactId>
+                <version>2.4</version>
+                <configuration>
+                    <archive>
+                        <manifestEntries>
+                            <Automatic-Module-Name>org.bukkit</Automatic-Module-Name>
+                        </manifestEntries>
+                    </archive>
+                </configuration>
+            </plugin>
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-shade-plugin</artifactId>