feat: add Ghostty terminal support (#225)

Add shipwright runner for Ghostty terminal emulator with example themes.

- Add ghostty.lua runner with Ghostty-specific color format
- Update init.lua to include ghostty in runner_files
- Add zenbones_dark and zenbones_light example themes

Ghostty uses a similar format to Kitty but with `=` separators and
`palette = N=COLOR` syntax for the 16 ANSI colors.

Tested and working with Ghostty terminal.

extras/ghostty/seoulbones_light

@@ -0,0 +1,37 @@
+# This file is auto-generated by shipwright.nvim
+# Ghostty color configuration
+# See: https://ghostty.org/docs/config/reference
+# Basic colors
+foreground = "#555555"
+background = "#E2E2E2"
+# Selection colors
+selection-foreground = "#555555"
+selection-background = "#CCCCCC"
+# Cursor colors
+cursor-color = "#555555"
+cursor-text = "#E2E2E2"
+# The basic 16 colors
+# black
+palette = 0=#E2E2E2
+palette = 8=#BFBABB
+# red
+palette = 1=#DC5284
+palette = 9=#BE3C6D
+# green
+palette = 2=#628562
+palette = 10=#487249
+# yellow
+palette = 3=#C48562
+palette = 11=#A76B48
+# blue
+palette = 4=#0084A3
+palette = 12=#006F89
+# magenta
+palette = 5=#896788
+palette = 13=#7F4C7E
+# cyan
+palette = 6=#008586
+palette = 14=#006F70
+# white
+palette = 7=#555555
+palette = 15=#777777