Update Intellij Platform to newest version

[johanneswolfgruber]

Is your feature request related to a problem? Please describe.
The Jetbrains Rider version currently uses Intellij Platform v2.0.1. At the time of writing this, the newest version is 2.1.0, which contains breaking changes, thus it was not included in my PR for issue #514.

Describe the solution you'd like
Intellij Platform is updated to the newest version from: https://github.com/JetBrains/intellij-platform-gradle-plugin/releases

Additional context
The errors I got when trying to update are:

src/XamlStyler.Extension.Rider/rider/main/kotlin/xavalon/plugins/xamlstyler/rider/XamlStylerComponent.kt:15:50 Unresolved reference 'xaml'.

src/XamlStyler.Extension.Rider/rider/main/kotlin/xavalon/plugins/xamlstyler/rider/XamlStylerComponent.kt:40:33 Unresolved reference 'XamlLanguage'.