Add Autoscale configuration conceptual page
Create a top level page for the Autoscaler executors based on the structure agreed here and refactor Instance and Docker Autoscaler executor pages.
# Autoscale configuration
Intro/description
- What autoscale is
- Why use it
- How it works (incl. diagram)
- List of executors for autoscaling
## Get started
1. Prepare the environment -- Removes duplicated content in executor pages.
- Select a fleeting plugin
- Install AWS fleeting plugin
2. Configure the type of executor
- Docker autoscaler -- link to Docker autoscaler executor page
- Instance executor -- link to Instance executor page
## Autoscale glossary (or we can have a specific glossary topic in each executor, or both!)
Edited by Fiona Neill