This PR makes changes to how the project overview skeleton screen works.
Important changes:
- Add skeleton screens to missing elements, creating a more
comprehensive loading screen
- Split the page into different loading sections, so that we can load
the table when we fetch the next page without affecting the rest of the
page.
https://www.loom.com/share/e5d30dc897ac488ea80cfae11ffab646
Next steps:
* Hide bar if total is less than 25
* Add FE testing
## About the changes
Refactoring the colors for the light theme to be much easier to continue
with dark mode
This is the first step to finish dark mode
https://linear.app/unleash/project/[low][s][alpha]-dark-mode-in-unleash-admin-ui-31b407d13c4b/1
This PR uses `main-theme` as a placeholder for `dark-theme` for now due
to the new changes. Still need to set the correct values here.
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Co-authored-by: Nuno Góis <github@nunogois.com>
