Update readme with quickstart

Author: Matthiee

README.md

@@ -1,2 +1,44 @@
 # FinancialModelingPrep.NET
 C# API Client For Financial Modeling Prep API written in .NET 5
+
+## Installation
+```powershell
+PM> Install-Package MatthiWare.FinancialModelingPrep
+```
+
+# Quick Start
+
+Register FinancialModelingPrepApiClient in Dependency Injection provider
+
+``` csharp
+Services.AddFinancialModelingPrepApiClient(new FinancialModelingPrepOptions() 
+{
+    ApiKey = "API-KEY-HERE"
+});
+```
+
+Resolve FMP API Client
+
+``` csharp
+var apiClient = ServiceProvider.GetRequiredService<IFinancialModelingPrepApiClient>();
+
+// do something with apiClient like getting the latest Apple Stock Quote
+var quoteResult = await api.CompanyValuation.GetQuoteAsync("AAPL");
+```
+
+All API Responses are wrapped in an `ApiResponse<T>` object.
+
+``` csharp
+var quoteResult = await api.CompanyValuation.GetQuoteAsync("AAPL");
+
+// Display Apple Stock Quote
+if (!quoteResult.HasError)
+{
+   Console.WriteLine($"$AAPL is currently trading at: {quoteResult.Data.Price}");
+} 
+else 
+{
+   Console.WriteLine($"Error Message: {quoteResult.Error}");
+}
+```
+