SPIGOT-7809: Add ShieldMeta

By: Doc <nachito94@msn.com>

paper-api/src/main/java/org/bukkit/inventory/meta/ShieldMeta.java

@@ -0,0 +1,27 @@
+package org.bukkit.inventory.meta;
+
+import org.bukkit.DyeColor;
+import org.jetbrains.annotations.Nullable;
+
+public interface ShieldMeta extends BannerMeta {
+
+    /**
+     * Gets the base color for this shield.
+     *
+     * @return the base color or null
+     */
+    @Nullable
+    DyeColor getBaseColor();
+
+    /**
+     * Sets the base color for this shield.
+     * <br>
+     * <b>Note:</b> If the shield contains a
+     * {@link org.bukkit.block.banner.Pattern}, then a null base color will
+     * retain the pattern but default the base color to {@link DyeColor#WHITE}.
+     *
+     * @param color the base color or null
+     */
+    void setBaseColor(@Nullable DyeColor color);
+
+}