A new "shareCode" field is generated for each entry, and allows
unlogged users to access the entry through the /shared endpoint.
This feature is particularly useful to share articles from miniflux
to third-party users without having them to visit the original source.
The image proxy is disabled and special cache headers are proposed in
the shared page to avoid denial of service.
- Use CSS variables instead of inherence
- Rename default theme to "Light - Serif"
- Rename Black theme to "Dark - Serif"
- Rename "Sans-Serif" theme to "Light - Sans Serif"
- Add "System" theme that use system preferences: Dark or Light
- Add Serif and Sans-Serif variants for each color theme
