Add DisplayInfo API

[Biswa96]

Fixes #595

[Rudxain]

/data/data/com.termux/files/usr/libexec/termux-api-broadcast DisplayInfo

My stdout:

[
  {
    "Name": "Built-in Screen",
    "DisplayId": 0,
    "AppVsyncOffset": 0,
    "PresentationDeadline": 17666667,
    "RefreshRate": 60.0,
    "Rotation": 0,
    "SupportedModes": [
      {
        "ModeId": 1,
        "PhysicalHeight": 2400,
        "PhysicalWidth": 1080,
        "RefreshRate": 60.0
      }
    ],
    "HdrCapabilities": {
      "DesiredMaxAverageLuminance": 500.0,
      "DesiredMaxLuminance": 500.0,
      "DesiredMinLuminance": 0.0
    },
    "DisplayMetrics": {
      "Density": 3.375,
      "DensityDPI": 540,
      "HeightPixels": 2321,
      "ScaledDensity": 3.375,
      "WidthPixels": 1080,
      "xDPI": 409.4320068359375,
      "yDPI": 411.8909912109375
    }
  }
]