Clean up WorkManager usages a bit

app/src/main/java/eu/kanade/tachiyomi/util/system/WorkManagerExtensions.kt

@@ -0,0 +1,13 @@
+package eu.kanade.tachiyomi.util.system
+
+import android.content.Context
+import androidx.work.WorkInfo
+import androidx.work.WorkManager
+
+val Context.workManager: WorkManager
+    get() = WorkManager.getInstance(this)
+
+fun WorkManager.isRunning(tag: String): Boolean {
+    val list = this.getWorkInfosByTag(tag).get()
+    return list.any { it.state == WorkInfo.State.RUNNING }
+}