fix imports

Author: andiwand

src/main/kotlin/app/opendocument/ConanInstallTask.kt

@@ -26,6 +26,7 @@ import org.gradle.api.provider.Property
 import org.gradle.api.provider.Provider
 import org.gradle.api.tasks.Exec
 import org.gradle.api.tasks.Input
+import org.gradle.api.tasks.Optional
 import org.gradle.api.tasks.OutputDirectory
 import org.gradle.api.tasks.OutputFile