feat: allow setting null option values to clear any set state

Author: zml2008

src/main/java/net/kyori/option/OptionState.java

@@ -142,7 +142,7 @@ interface Builder {
      * @param <V> the value type
      * @since 1.0.0
      */
-    <V> Builder value(final Option<V> option, final V value);
+    <V> Builder value(final Option<V> option, final @Nullable V value);
 
     /**
      * Apply all values from the existing option state.

src/main/java/net/kyori/option/OptionStateImpl.java

@@ -176,15 +176,16 @@ public OptionState build() {
     }
 
     @Override
-    public <V> Builder value(final Option<V> option, final V value) {
-      if (!this.schema.has(option)) {
+    public <V> Builder value(final Option<V> option, final @Nullable V value) {
+      if (!this.schema.has(requireNonNull(option, "option"))) {
         throw new IllegalStateException("Option '" + option.id() + "' was not present in active schema");
       }
 
-      this.values.put(
-        requireNonNull(option, "flag"),
-        requireNonNull(value, "value")
-      );
+      if (value == null) {
+        this.values.remove(option);
+      } else {
+        this.values.put(option, value);
+      }
       return this;
     }