SPIGOT-2540: Add nullability annotations to entire Bukkit API

By: Darkyenus <darkyenus@gmail.com>

paper-api/pom.xml

@@ -83,6 +83,13 @@
             <version>1.23</version>
             <scope>compile</scope>
         </dependency>
+        <!-- annotations -->
+        <dependency>
+            <groupId>org.jetbrains</groupId>
+            <artifactId>annotations-java5</artifactId>
+            <version>17.0.0</version>
+            <scope>provided</scope>
+        </dependency>
         <!-- testing -->
         <dependency>
             <groupId>junit</groupId>
@@ -96,6 +103,12 @@
             <version>1.3</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.ow2.asm</groupId>
+            <artifactId>asm-tree</artifactId>
+            <version>7.1</version>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 
     <build>