Update UploadDocuments to be virtual (#42)

Allows developers the ability to trigger various actions when an upload is made to Azure.

Author: povadek

src/Kentico.Xperience.AzureSearch/Indexing/BaseAzureSearchIndexingStrategy.cs

@@ -42,7 +42,7 @@ namespace Kentico.Xperience.AzureSearch.Indexing;
     public IList<SearchField> GetSearchFields() => fieldBuilder.Build(typeof(TSearchModel));
 
     /// <inheritdoc />
-    public async Task<int> UploadDocuments(IEnumerable<IAzureSearchModel> models, SearchClient searchClient)
+    public virtual async Task<int> UploadDocuments(IEnumerable<IAzureSearchModel> models, SearchClient searchClient)
     {
         var batch = new IndexDocumentsBatch<TSearchModel>();