PR that fixes some of these aspects: #3397

Potential Improvements to be made

• Indicate pages that open external screens more clearly in the page list, by an icon, text, or both
• Make scrollbars thicker for easier use
• Hide search bar clear button when nothing is searched
• Make search bar text have more contrast
• Inset the whole UI into a centered container of reasonable width on large screens
• When inset, space between search bar/close button and page list/search bar?
• Disabled tickboxes don't show the right enablement state
• per-option and global reset buttons
• Clicking on mod headers in the page list should jump to the start of their options in the option list
• moving the window from one monitor to the other while the settings ui is open causes a crash because it tries to read a video mode with an index higher than the number of video modes on the new screen
• Adjust spacing in multiple places in the UI to accomodate horizontal and vertical external margins on the content area (separately)

API Improvements

• Custom update flags (like renderer reload) and registering flag-related runners globally
• Post-save hooks that are syntactic sugar for a unique flag per option example
• API for mods to open the config screen and jump to a certain page for use in mod menu integrations. example
• Document Option Overlay and Replacement API usage
• Graphics presets to match vanilla
• Customization of presents? Adding new presets? adding options from mods to presets through the api?