packets: Add support for custom actions

libraries/packets/packets-api/src/main/java/de/oliver/fancysitula/api/dialogs/actions/FS_DialogCustomAction.java

@@ -0,0 +1,32 @@
+package de.oliver.fancysitula.api.dialogs.actions;
+
+import org.intellij.lang.annotations.Subst;
+import org.jetbrains.annotations.Nullable;
+
+public class FS_DialogCustomAction implements FS_DialogActionButtonAction {
+
+    private String id;
+    private @Nullable String additions;
+
+    public FS_DialogCustomAction(String id, String additions) {
+        this.id = id;
+        this.additions = additions;
+    }
+
+    @Subst("")
+    public String getId() {
+        return id;
+    }
+
+    public void setId(String id) {
+        this.id = id;
+    }
+
+    public @Nullable String getAdditions() {
+        return additions;
+    }
+
+    public void setAdditions(@Nullable String additions) {
+        this.additions = additions;
+    }
+}