Fix spigot plugin.yml version

Author: TBlueF

implementations/spigot/src/main/resources/plugin.yml

@@ -1,7 +1,7 @@
 name: BlueMap
 description: "A 3d-map of your Minecraft worlds view-able in your browser using three.js (WebGL)"
 main: de.bluecolored.bluemap.bukkit.BukkitPlugin
-version: ${version}
+version: "${version}"
 api-version: 1.13
 author: "Blue (TBlueF / Lukas Rieger)"
 website: "https://github.com/BlueMap-Minecraft"