This PR adds support for loading user themes in Zed.
Themes are loaded from the `themes` directory under the Zed config:
`~/.config/zed/themes`. This directory should contain JSON files
containing a `ThemeFamilyContent`.
Here's an example of the general structure of a theme family file:
```jsonc
{
"name": "Vitesse",
"author": "Anthony Fu",
"themes": [
{
"name": "Vitesse Dark Soft",
"appearance": "dark",
"style": {
"border": "#252525",
// ...
}
}
]
}
```
Themes placed in this directory will be loaded and available in the
theme selector.
Release Notes:
- Added support for loading user themes from `~/.config/zed/themes`.