IntelliJ Plugin

[christianhelle]

Create an IntelliJ plugin under the src\IntelliJ folder that matches the features in the VSCode extension in src/VSCode. This needs to run in the latest version of JetBrains Rider, version 2025.1.2.

Create some scripts so that I can conveniently verify that the plugin builds and so that I can test it easily.

This will need to build on Github Actions so create a workflow for it. Use the images\icon.png icon if the plugin needs it.

Create a README on the IntelliJ folder that describes the plugins features.

Update the main README with details about the IntelliJ plugin.