Persist settings

[jonatan-ivanov]

There are quite a few settings that users can specify. Unfortunately, they reset when the page is reloaded:

• Milky Way
• DSS
• Meridian Line
• Ecliptic Line
• Whether the navigation drawer (left sidebar) is visible or not (clicking on the hamburger menu)
• Location, see Remember location #253
• Constellations
• Constellations Art
• Atmosphere
• Landscape
• Azimuthal Grid
• Equatorial Grid
• Deep Sky Objects
• Night Mode

It would be nice to store these settings (e.g.: in the browser's local storage) and read it back load-time so that users don't need to modify these settings every single time if they don't want to use the defaults.