Remove WiFi clients overlay usage examples from README

Deleted configuration and example usage sections for the WiFi clients overlay from the README to streamline documentation. Updated section heading for GeoJSON handling. Also updated netjsonmap-multipleTiles.gif in docs/gifs.

Author: cestercian

README.md

@@ -488,31 +488,6 @@ Looking for configuration details? See the inline docs and type hints in the sou
 
 It's possible to render small colored circles around each node to represent the amount of connected WiFi clients. The overlay counts WiFi clients as a single total. This helper draws on the same ZRender layer as the graph, so the markers follow pan/zoom/force layout without extra work and do not call `setOption` during the main render.
 
-### Configuration
-
-- **Example**: See `public/example_templates/netjsongraph-wifi-clients.html` with dataset `public/assets/data/netjsongraph-wifi-clients.json`
-
-#### Example Usage
-
-```javascript
-const graph = new NetJSONGraph("../assets/data/netjsongraph-wifi-clients.json", {
-  render: "graph",
-  onReady() {
-    // Attach the client overlay once the graph is ready
-    this.attachClientsOverlay({
-      // --- Optional configuration ---
-      radius: 5, // Radius of each client dot in pixels
-      gap: 3, // Distance from the node's edge to the first ring of dots
-      colors: {
-        wifi: "#d35454",
-      },
-      minZoomLevel: 1, // Only show dots when zoom level is at or above this value
-    });
-  },
-});
-graph.render();
-```
-
 For a live demo, see the [WiFi Clients Graph example](https://openwisp.github.io/netjsongraph.js/examples/netjsongraph-wifi-clients.html).
 
 #### Data Format
@@ -523,34 +498,7 @@ The number of dots rendered around a node is determined by the `clients` field i
   - If it's an Array, its length is used as the client count (and the sidebar lists Client [i] entries, e.g., MAC addresses).
   - If it's a Number, the value is used directly as the count.
 
-**Example Node Data**:
-
-```javascript
-{
-  "nodes": [
-    {
-      "id": "A",
-      "label": "Node A",
-      // Shows 1 primary client dot. Displays details in the sidebar.
-      "clients": [{"mac": "d8:5d:4c:f1:aa:62"}]
-    },
-    {
-      "id": "B",
-      "label": "Node B",
-      // Shows 2 primary client dots.
-      "clients": [{"mac": "..."}, {"mac": "..."}]
-    },
-    {
-      "id": "C",
-      "label": "Node C",
-      // Shows 1 primary client dot.
-      "clients": 1
-    }
-  ]
-}
-```
-
-### GeoJSON handling
+## GeoJSON handling
 
 netjsongraph.js will now **always** convert GeoJSON input into an internal
 NetJSON‐like structure (`nodes` / `links`). The original GeoJSON object is kept