Add checkstyle validation for formatting, fix issues

config/checkstyle/checkstyle.xml

@@ -53,5 +53,13 @@
     <!-- <module name="PackageName"/> Unlikely that we would miss this in a PR -->
     <module name="ParameterName"/>
     <!-- <module name="TypeName"/> Unlikely that we would miss this in a PR -->
+    <!-- Validate assignment operators -->
+    <module name="WhitespaceAround">
+      <property name="tokens" value="ASSIGN"/>
+    </module>
+  </module>
+  <!-- Validate that command annotations are formatted correctly -->
+  <module name="RegexpMultiline">
+    <property name="format" value="^( +)@(Arg|Switch|Command)\(.*?\n\1 {5,}"/>
   </module>
 </module>

worldedit-core/src/main/java/com/sk89q/worldedit/command/BiomeCommands.java

@@ -19,8 +19,6 @@
 
 package com.sk89q.worldedit.command;
 
-import static com.sk89q.worldedit.command.util.Logging.LogMode.REGION;
-
 import com.sk89q.worldedit.EditSession;
 import com.sk89q.worldedit.LocalSession;
 import com.sk89q.worldedit.WorldEdit;
@@ -59,6 +57,8 @@ import java.util.Objects;
 import java.util.Set;
 import java.util.stream.Collectors;
 
+import static com.sk89q.worldedit.command.util.Logging.LogMode.REGION;
+
 /**
  * Implements biome-related commands such as "/biomelist".
  */