docs: 📝 Add context menu doc

apps/docs/docs/editor/context-menu.mdx

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+# Context menu
+
+You can right-click on different elements on the builder to trigger a menu with different actions.
+
+If you right-click on a group, you will see a menu with the following options:
+
+<img src="/img/group-context-menu.png" width="500" alt="Context menu" />
+
+- **Duplicate** to create a duplicated group with the same blocks and settings
+- **Delete** to remove the group
+
+If you right-click on a block, you will see a menu with the following options:
+
+- **Duplicate** to create a duplicated block below the duplicated one with the same settings
+- **Delete** to remove the block
+
+If you right-click on an edge, you will see a menu with the following options:
+
+<img src="/img/edge-context-menu.png" width="500" alt="Context menu" />
+
+- **Delete** to remove the edge