add doc about protocols

README.md

@@ -6,11 +6,30 @@
 
 1. Install the extension
 2. open `style.json` in editor
-3. open command palette and run `Maplibre: Viewer`
+3. open command palette and run `MapLibre: Viewer`
     - ![](https://github.com/Kanahiro/maplibre-vscode-extension/blob/main/doc/palette.png?raw=true)
 4. Viewer will open in new tab. When edit `style.json`, the viewer will update automatically.
     - ![](https://github.com/Kanahiro/maplibre-vscode-extension/blob/main/doc/viewer.png?raw=true)
 
+### Available protocols
+
+- `http://path/to/file`
+- `https://path/to/file`
+- `pmtiles://path/to/file.pmtiles`
+
+```json
+"sources": {
+    "openmaptiles": {
+      "type": "vector",
+      "url": "pmtiles://https://tile.openstreetmap.jp/static/planet-20240729.pmtiles"
+    },
+    "takeshima": {
+      "type": "vector",
+      "url": "https://tile.openstreetmap.jp/data/takeshima.json"
+    }
+},
+```
+
 ## attribution
 
 - icon: <https://github.com/maplibre/maplibre.github.io/blob/main/static/img/maplibre%20old%20profile.png>