Don't strip leading - off of config file vmargs

The writer for config.json only adds a - if one isn't present. This means to pass a vm arg such as --add-opens via the config it would require ---add-opens, which is strange. Instead, don't strip leading - at all from the config.

src/main/java/com/badlogicgames/packr/PackrConfig.java

@@ -178,11 +178,7 @@ private void readConfigJson(File configJson) throws IOException {
 			List<String> vmArgs = toStringArray(json.get("vmargs").asArray());
 			this.vmArgs = new ArrayList<>();
 			for (String vmArg : vmArgs) {
-				if (vmArg.startsWith("-")) {
-					this.vmArgs.add(vmArg.substring(1));
-				} else {
-					this.vmArgs.add(vmArg);
-				}
+				this.vmArgs.add(vmArg);
 			}
 		}
 		if (json.get("minimizejre") != null) {