Document Istio adapter changes TP11

There a few changes needed, creating an epic to group them all. Upstream docs can be taken as reference. I'll describe all changes here, feel free to create issues for individual tasks (a couple created already).

All the changes in the upstream docs can be found here
https://github.com/3scale/3scale-istio-adapter/compare/v0.5.0...v0.6.0#files_bucket

Detail

Features

• Enabling policies (I thought this was already in the product docs, but mentioning just in case). Suggested to link link https://maistra.io/docs/troubleshooting/troubleshooting_policy/ instead to Istio docs
• Changes in modifying the handler configuration
• New paragraph in 'Applying patterns'
• API Key pattern – change of template name
• OIDC - new
• Hybrid pattern - some updates
• Generating sample custom resources - some updates

CLI

• -v new to output version
• added example to generate templates from URL