Latest Cake Build emits warning: The assembly 'Cake.DocFx, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' is referencing an older version of Cake.Core (1.0.0). For best compatibility it should target Cake.Core version 2.0.0.

## Expected Behavior
Cake.Core 2.0 is supported.

## Current Behavior
Cake.Core 2.0 is not supported.

## Possible Solution
Finish (or provide guidance) for the PR which I will open against this issue.

## Automated Steps to Reproduce
1. Run the following PowerShell from an environment with .net 5.0 installed.
```powershell
git clone https://github.com/ericburcham/cake-docfx-warning.git
cd cake-docfx-warning
dotnet tool restore
dotnet cake
```
2. Observe the warning message in the cake build output.

## Manual Steps to Reproduce
1. Create a git repo and install the latest version of the Cake dotnet tool.
3. Add a Visual Studio solution and one or more projects.
4. Configure DocFx to build documentation for your solution.
5. Edit your build.cake file to include this plugin.
6. Create a Cake Task to invoke DocFxBuild("./path/to/docfx.json")
7. Invoke the task.
8. Observe the warning message in the cake build output.

## Context
I am using Cake.DocFx in a repository at work and on build servers, and I am concerned I will have compatibility issues. I have not actually observed any yet. I'm just trying to be proactive.

## Your Environment
* Addin version used: 1.0.0
* Cake Version used: cake.tool 2.0.0
* Operating System: Windows 11 desktop, Windows Server 2022.

Start with the provided PowerShell reproduction: clone the repository, restore the .NET tool, and run dotnet cake to confirm the warning. Review how Cake.DocFx 1.0.0 references Cake.Core, then verify the build completes without the older-version warning when used with cake.tool 2.0.0.

Written by the indexing model from the issue text.