added ui elements for update reminder

src/main/resources/fxml/update_reminder.fxml

@@ -0,0 +1,54 @@
+<?xml version="1.0" encoding="UTF-8"?>
+
+<?import javafx.scene.layout.*?>
+<?import javafx.scene.control.ButtonBar?>
+<?import javafx.geometry.Insets?>
+<?import javafx.scene.Group?>
+<?import javafx.scene.shape.Circle?>
+<?import org.cryptomator.ui.controls.FontAwesome5IconView?>
+<?import javafx.scene.control.Label?>
+<?import javafx.scene.control.Button?>
+<HBox xmlns:fx="http://javafx.com/fxml"
+	  xmlns="http://javafx.com/javafx"
+	  fx:controller="org.cryptomator.ui.updatereminder.UpdateReminderController"
+	  minWidth="450"
+	  maxWidth="450"
+	  minHeight="145"
+	  spacing="12"
+	  alignment="TOP_LEFT">
+	<padding>
+		<Insets topRightBottomLeft="12"/>
+	</padding>
+	<children>
+		<VBox>
+			<HBox>
+			<Group>
+				<StackPane>
+					<padding>
+						<Insets topRightBottomLeft="6"/>
+					</padding>
+					<Circle styleClass="glyph-icon-primary" radius="24"/>
+					<FontAwesome5IconView styleClass="glyph-icon-white" glyph="EXCLAMATION" glyphSize="24"/>
+				</StackPane>
+			</Group>
+
+		<VBox HBox.hgrow="ALWAYS">
+			<Label styleClass="label-large" text="%updateReminder.title" wrapText="true">
+				<padding>
+					<Insets bottom="6" top="6"/>
+				</padding>
+			</Label>
+			<Label text="%updateReminder.message" wrapText="true"/>
+			<Region VBox.vgrow="ALWAYS" minHeight="18"/>
+		</VBox>
+		</HBox>
+		<ButtonBar buttonMinWidth="120" buttonOrder="CY">
+			<buttons>
+				<Button text="%updateReminder.notNow" ButtonBar.buttonData="CANCEL_CLOSE" cancelButton="true" onAction="#cancel"/>
+				<Button text="%updateReminder.yesOnce" ButtonBar.buttonData="YES" onAction="#once"/>
+				<Button text="%updateReminder.yesAutomatically" ButtonBar.buttonData="YES" defaultButton="true" onAction="#automatically" />
+			</buttons>
+		</ButtonBar>
+		</VBox>
+	</children>
+</HBox>

src/main/resources/i18n/strings.properties

@@ -492,4 +492,10 @@ quit.lockAndQuitBtn=Lock and Quit
 # Forced Quit
 quit.forced.message=Some vaults could not be locked
 quit.forced.description=Locking vaults was blocked by pending operations or open files. You can force lock remaining vaults, however interrupting I/O may result in the loss of unsaved data.
-quit.forced.forceAndQuitBtn=Force and Quit
+quit.forced.forceAndQuitBtn=Force and Quit
+# Update Reminder
+updateReminder.title=Check for Updates?
+updateReminder.message=Would you like Cryptomator to check whether an update is available?
+updateReminder.notNow=Not now
+updateReminder.yesOnce=Yes, once
+updateReminder.yesAutomatically=Yes, automatically