Feature/graphql web UI (#649)

* Add "server" to "checkForUpdate" logic names

* Use "webUIRoot" as default path for "getLocalVersion"

* Use local version as default version for "isUpdateAvailable"

* Return the version with the webUI update check

* Update WebinterfaceManager to be async

* Add query, mutation and subscription for webUI update

* Catch error and return default error value for missing local WebUI version

server/src/main/kotlin/suwayomi/tachidesk/graphql/subscriptions/InfoSubscription.kt

@@ -0,0 +1,11 @@
+package suwayomi.tachidesk.graphql.subscriptions
+
+import kotlinx.coroutines.flow.Flow
+import suwayomi.tachidesk.graphql.types.WebUIUpdateStatus
+import suwayomi.tachidesk.server.util.WebInterfaceManager
+
+class InfoSubscription {
+    fun webUIUpdateStatusChange(): Flow<WebUIUpdateStatus> {
+        return WebInterfaceManager.status
+    }
+}