postmarketOS/phosh-mobile-settings integration

Currently, there is no easy way for applications to install settings that then show up in the system's settings app on desktop Linux systems. As part of bringing desktop Linux to mobile phones in postmarketOS, we have created a "tweaks" app for phone-specific configuration options. With this project, the options in this tweaks app will be converted to a format described by a specification which settings apps then can implement. This in turn is part of a broader effort to make desktop Linux suitable for running on mobile phones as a means to create an operating system for phones without excessive user tracking or built-in ads, with a focus on the user instead of money.