Theme option changes don't reflect immediately

[kaidesu]

Describe the issue

When working on theme options and adding/changing values, you must go through this process for the changes to reflect:

1. Delete the storage/themes/YourTheme.json file
2. Load a page that references your theme option with the theme_option() helper function
3. Visit the theme customizer in the control panel

Expected behavior

Obviously this is a very tedious process. Currently the only thing managing the values of theme options is the theme_option helper function itself. This needs to be done for the user automatically when visiting the theme customizer page.

Version and browser

Version: v6.0.0 beta 6

Bug report checklist

• I have filled out as much information as I can
• I have detailed how the issue can be reproduced
• I have searched for existing issues and to the best of my knowledge this is not a duplicate