add csharp snippets

snippets/csharp/FiatCurrencies.cs

@@ -0,0 +1,39 @@
+using Breez.Sdk;
+
+public class FiatCurrenciesSnippets
+{
+    public void ListFiatCurrencies(BlockingBreezServices sdk)
+    {
+        // ANCHOR: list-fiat-currencies
+        try
+        {
+            var fiatCurrencies = sdk.ListFiatCurrencies();
+        }
+        catch (Exception)
+        {
+            // Handle error
+        }
+        // ANCHOR_END: list-fiat-currencies
+    }
+
+    public void FetchFiatRates(BlockingBreezServices sdk)
+    {
+        // ANCHOR: fetch-fiat-rates
+        try
+        {
+            var fiatRates = sdk.FetchFiatRates();
+        }
+        catch (Exception)
+        {
+            // Handle error
+        }
+        // ANCHOR_END: fetch-fiat-rates
+    }
+
+    public void GetFiatCurrenciesAndRates(BlockingBreezServices sdk)
+    {
+        // ANCHOR: get-fiat-currencies-and-rates
+        // TODO
+        // ANCHOR_END: get-fiat-currencies-and-rates
+    }
+}