Update plugin spring-nullability to v0.0.9 (#450)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>
Co-authored-by: Roberto Cella <[email protected]>

Author: renovate[bot]

gradle/libs.versions.toml

@@ -15,4 +15,4 @@ telegram-bot-api = "com.github.pengrad:java-telegram-bot-api:9.2.1"
 tika = "org.apache.tika:tika-core:3.2.3"
 
 [plugins]
-spring-nullability = "io.spring.nullability:0.0.8"
+spring-nullability = "io.spring.nullability:0.0.9"

src/test/java/com/github/stickerifier/stickerify/ResourceHelper.java

@@ -2,8 +2,11 @@
 
 import static org.junit.jupiter.api.Assertions.assertNotNull;
 
+import org.jspecify.annotations.NullMarked;
+
 import java.io.File;
 
+@NullMarked
 public final class ResourceHelper {
 
 	public static File loadResource(String filename) {

src/test/java/com/github/stickerifier/stickerify/junit/package-info.java

@@ -0,0 +1,4 @@
+@NullMarked
+package com.github.stickerifier.stickerify.junit;
+
+import org.jspecify.annotations.NullMarked;