Add nuget download badge to README.md

Author: markatk

README.md

@@ -1,5 +1,6 @@
 # AlternateLife.RageMP.Net
 ![Build status](https://teamcity.alternate-life.de/app/rest/builds/buildType:(id:RageMP_NETCore_Release)/statusIcon)
+[![NuGet](https://img.shields.io/nuget/dt/AlternateLife.RageMP.Net.svg)](https://www.nuget.org/packages/AlternateLife.RageMP.Net)
 
 AlternateLife.RageMP.Net is an alternative server-side .NET Core 2.1 implementation for [RAGE Multiplayer](https://rage.mp). This library targets more advanced developers which are more familiar with the RAGE Multiplayer server API and its features. It offers a mostly asynchronous API to interact with, so a thread-safe access to the native API is always guaranteed.
 
@@ -105,4 +106,4 @@ FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-SOFTWARE.
+SOFTWARE.