NEW: Pre-migration checklists

[#1]

To help ensure your migration is successful, we've put together a list of common things to check for before attempting a test or production migration. 

Use these checklists to ensure you, and your data, are ready to migrate.

• Confluence pre-migration checklist
• Jira pre-migration checklist

[Bastian Stehmann]

Hi @Maren ,

Thanks for getting this together. I think its really helpful to have this two on one place as a starting point.