Add Reload CSS button
Describe what this pull request is trying to achieve.
Adds a Reload CSS button to the settings page. Allows changing webui's style.css or extension CSS without needing to restart the entire webui
Additional notes and description of your changes
The CSS is saved in the backend too, so it will be preserved the page is reloaded
Environment this was tested in
List the environment you have developed / tested this on. As per the contributing page, changes should be able to work on Windows out of the box.
- OS: Windows
- Browser: Chrome
- Graphics card: NVIDIA RTX 3090
Screenshots or videos of your changes

Actions might be a better place for this.
https://github.com/AUTOMATIC1111/stable-diffusion-webui/blob/2f129ef490e175943dd50163015dd1e6fc8d49f0/modules/ui.py#L1526-L1532
Or down at the bottom next to Reload UI.
https://github.com/AUTOMATIC1111/stable-diffusion-webui/blob/64da5c46ef0d68b9048747c2e0d46ce3495f9f29/html/footer.html#L8
I think a better solution would be to refer to independent css files as they are on disk, same as it's done with javascript, so that there is necessity to do anything serverside to update them.
If not, then yes, I also think the button should be in Actions.
See #8942
Since the change for independent css files is merged in #9031 and this is incompatible with it, I'm closing the PR.