[Feature Request] Support ~ in playlist

In retroarch.cfg it is possible to use ~ to denote a path to the current user directory.

For example

rgui_browser_directory = "~/games"
rgui_config_directory = "~/.config/retroarch/config"

This makes it easy to synchronize the configuration file between different devices.

Playlists on the other hand, does not seem to support this feature

Example

{
    "version": "1.5",
    "default_core_path": "",
    "default_core_name": "",
    "label_display_mode": 0,
    "right_thumbnail_mode": 0,
    "left_thumbnail_mode": 0,
    "sort_mode": 0,
    "items": [
        {
            "path": "~/games/psp/supertux/Supertux/EBOOT.PBP",
            "label": "SuperTux PSP",
            "core_name": "Sony - PlayStation Portable (PPSSPP)",
            "core_path": "~/.config/retroarch/cores/ppsspp_libretro.so",
            "crc32": "00000000|crc",
            "db_name": "Sony - PlayStation Portable"
        }
    ]
}

I get the error message "Failed to load from playlist".

The issue provides retroarch.cfg and a playlist JSON example, but no source file or test. Start by finding playlist loading and the existing path handling for ~ in configuration; done means a playlist using ~ loads successfully without breaking absolute paths.