docs: add code samples (#614)

README.md

@@ -51,6 +51,38 @@ const client = new APIClient(APIClient.URL_LIVE, {
 });
 ```
 
+Search for an IG epic code
+
+```
+const response = await client.rest.market.searchMarkets('BITCOIN');
+console.log(JSON.stringify(response, null, 4));
+console.log(response.markets[0].epic);
+```
+
+Subscribe to realtime candles updates with IG epic codes
+
+```
+const epics = [ 'CS.D.BITCOIN.OPTCALL.IP' ];
+
+client.stream.subscribeCandles(epics, Resolution.SECOND, (epic, candle) => {
+  console.log(epic);
+  console.log(candle)
+});
+```
+
+Retrieve historical data of an IG epic code
+
+```
+const prices = await client.rest.market.price.getPrices('CS.D.BITCOIN.OPTCALL.IP', Resolution.DAY, 5);
+console.log(JSON.stringify(prices, null, 4));
+
+```
+
+Show available resolutions
+```
+import { APIClient, Resolution } from 'ig-trading-api';
+console.log(Resolution)
+```
 ## Resources
 
 - [IG REST Trading API Reference](https://labs.ig.com/rest-trading-api-reference)