1. Create a Project
To create a plugin project:
In Visual Studio, create a new project of the Class Library (Visual C#) type.
Reference ReSharper SDK. It is distributed via NuGet, so, you can reference the SDK via the package manager:
Open Tools | NuGet Package Manager | Manage NuGet Packages for Solution….
In the opened window, find JetBrains.ReSharper.SDK.
In Version, select the package version. It must match the ReSharper version your plugin targets.
Build the project to get the .dll file.
Now, you should create the NuGet package for the plugin.