Could not get unknown property 'ProGuardTask'

I want to add ProGuard obfuscation to my Java project, to automatically obfuscate the JAR when building it. I created a default build.gradle file, added my dependencies and pasted in what ProGuard has on their website. I keep getting an error.

• ProGuard GitHub with Gradle task: https://github.com/Guardsquare/proguard
• ProGuard Gradle detailed setup page: https://www.guardsquare.com/manual/setup/gradle

The error:

Could not get unknown property 'ProGuardTask' for root project 'MCPets-multipet-gradle' of type org.gradle.api.Project.

build.gradle file:

// ProGuard
buildscript {
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath 'com.guardsquare:proguard-gradle:7.7.0'
    }
}

plugins {
    id 'java'
}

group 'org.example'
version '1.0-SNAPSHOT'

repositories {
    mavenCentral()
    maven{url = 'https://hub.spigotmc.org/nexus/content/repositories/snapshots/'}
    maven{url = 'https://repo.papermc.io/repository/maven-public/'}
    maven{url = 'https://libraries.minecraft.net/'}
    maven{url = 'https://mvn.lumine.io/repository/maven-public/'}
    maven{url = 'https://maven.enginehub.org/repo/'}
    maven{url = 'https://repo.extendedclip.com/content/repositories/placeholderapi/'}
    maven{url = 'https://oss.sonatype.org/content/repositories/snapshots'}
    maven{url = 'https://jitpack.io'}
}

dependencies {
    // Technical dependencies
    compileOnly("org.projectlombok:lombok:1.18.38")
    annotationProcessor("org.projectlombok:lombok:1.18.38")
    implementation 'com.google.code.gson:gson:2.8.9'

    // Minecraft dependencies
    implementation 'org.spigotmc:spigot-api:1.21-R0.1-SNAPSHOT'
    implementation 'io.papermc.paper:paper-api:1.21-R0.1-SNAPSHOT'

    // Plugin dependencies
    implementation 'io.lumine:Mythic-Dist:5.6.0-SNAPSHOT'
    implementation 'com.sk89q.worldguard:worldguard-bukkit:7.0.7-SNAPSHOT'
    implementation 'me.clip:placeholderapi:2.11.6'
    implementation 'net.luckperms:api:5.4'
    implementation 'com.ticxo.modelengine:ModelEngine:R4.0.6'
    implementation 'com.github.LoneDev6:api-itemsadder:3.6.1'
}



// ProGuard
tasks.register('proguard', ProGuardTask) {
    configuration file('proguard.pro')

    injars(tasks.named('jar', Jar).flatMap { it.archiveFile })

    // Automatically handle the Java version of this build.
    if (System.getProperty('java.version').startsWith('1.')) {
        // Before Java 9, the runtime classes were packaged in a single jar file.
        libraryjars "${System.getProperty('java.home')}/lib/rt.jar"
    }
    else {
        // As of Java 9, the runtime classes are packaged in modular jmod files.
        libraryjars "${System.getProperty('java.home')}/jmods/java.base.jmod", jarfilter: '!**.jar', filter: '!module-info.class'
        //libraryjars "${System.getProperty('java.home')}/jmods/....."
    }

    verbose

    outjars(layout.buildDirectory.file("libs/${baseCoordinates}-minified.jar"))
}

Solved!
All I needed to do is add import proguard.gradle.ProGuardTask at the top..