Added missing annotations

eco-api/src/main/java/com/willfp/eco/core/EcoPlugin.java

@@ -864,6 +864,7 @@ public abstract class EcoPlugin extends JavaPlugin implements PluginLike {
      * @param pluginName The name.
      * @return The plugin.
      */
+    @Nullable
     public static EcoPlugin getPlugin(@NotNull final String pluginName) {
         return Eco.get().getPluginByName(pluginName);
     }
@@ -873,6 +874,7 @@ public abstract class EcoPlugin extends JavaPlugin implements PluginLike {
      *
      * @return The set of names.
      */
+    @NotNull
     public static Set<String> getPluginNames() {
         return new HashSet<>(Eco.get().getLoadedPlugins());
     }