graphics: option to change monitor resolution (#689)

## Link to GitHub Issue or related Pull Request, if one exists
n/a

## Description of change
Add a new option under `Monitor` group to change the monitor resolution
before booting the game, very similar to how orientation / refresh rate
options work.

This would be useful for games like Polaris Chord that boots at current
resolution but manages to have graphical issues when not in 1080p.

## Testing

src/spice2x/launcher/options.cpp

@@ -1920,6 +1920,15 @@ static const std::vector<OptionDefinition> OPTION_DEFINITIONS = {
             {"3", "Landscape, Flipped"}
         },
     },
+    {
+        // ChangeResolution
+        .title = "Change Monitor Resolution",
+        .name = "changeres",
+        .desc = "Changes monitor resolution before booting the game.",
+        .type = OptionType::Text,
+        .setting_name = "1280,720",
+        .category = "Monitor"
+    },
     {
         .title = "AVS Log Level",
         .name = "loglevel",