macOS: Add support for quick terminal sizing configuration

Added C bindings for the already existing quick-terminal-size
configuration. Created a new QuickTerminalSize struct to hold these
values in Swift. Updated the QuickTerminal implementation to use the
user's configuration if supplied. Retains defaults. Also adds support to
customize the width of the quick terminal (height if quick terminal is
set to right or left).

include/ghostty.h

@@ -450,6 +450,14 @@ typedef struct {
   ghostty_config_color_s colors[256];
 } ghostty_config_palette_s;
 
+// config.QuickTerminalSize
+typedef struct {
+  uint8_t primary_type;    // 0 = none, 1 = percentage, 2 = pixels
+  float primary_value;
+  uint8_t secondary_type;  // 0 = none, 1 = percentage, 2 = pixels
+  float secondary_value;
+} ghostty_config_quick_terminal_size_s;
+
 // apprt.Target.Key
 typedef enum {
   GHOSTTY_TARGET_APP,