Block extensions only work if they are alphabetically sorted after editor

[AdrianFahrbach]

Describe the bug
Block extensions with plugin folders that are alphabetically sorted before editor don't work.

To Reproduce
Steps to reproduce the behavior:

1. Copy a block extension example to your plugins folder
2. Rename the block extension folder to something that is sorted before editor
3. Open the panel in your browser and look at the console. The error above should appear.

Expected behavior
The block extension should work

Kirby Version
3.5.0

Console output
Uncaught ReferenceError: editor is not defined

Desktop (please complete the following information):

• OS: macOS
• Browser: Chrome
• Version: 87