Added bool argument

src/main/java/com/mojang/brigadier/arguments/BoolArgumentType.java

@@ -0,0 +1,46 @@
+package com.mojang.brigadier.arguments;
+
+import com.mojang.brigadier.CommandDispatcher;
+import com.mojang.brigadier.context.CommandContext;
+import com.mojang.brigadier.context.CommandContextBuilder;
+import com.mojang.brigadier.context.FixedParsedArgument;
+import com.mojang.brigadier.context.ParsedArgument;
+import com.mojang.brigadier.exceptions.CommandException;
+import com.mojang.brigadier.exceptions.SimpleCommandExceptionType;
+
+public class BoolArgumentType implements ArgumentType<Boolean> {
+    public static final SimpleCommandExceptionType ERROR_INVALID = new SimpleCommandExceptionType("argument.bool.invalid", "Value must be true or false");
+
+    private BoolArgumentType() {
+    }
+
+    public static BoolArgumentType bool() {
+        return new BoolArgumentType();
+    }
+
+    public static boolean getBool(CommandContext<?> context, String name) {
+        return context.getArgument(name, Boolean.class);
+    }
+
+    @Override
+    public <S> ParsedArgument<S, Boolean> parse(String command, CommandContextBuilder<S> contextBuilder) throws CommandException {
+        int end = command.indexOf(CommandDispatcher.ARGUMENT_SEPARATOR);
+        String raw = command;
+        if (end > -1) {
+            raw = command.substring(0, end);
+        }
+
+        if (raw.equals("true")) {
+            return new FixedParsedArgument<>(raw, true);
+        } else if (raw.equals("false")) {
+            return new FixedParsedArgument<>(raw, false);
+        } else {
+            throw ERROR_INVALID.create();
+        }
+    }
+
+    @Override
+    public String getUsageText() {
+        return "bool";
+    }
+}