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/zenburned

@@ -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 = "#F0E4CF"
+background = "#404040"
+# Selection colors
+selection-foreground = "#F0E4CF"
+selection-background = "#746956"
+# Cursor colors
+cursor-color = "#F3EADB"
+cursor-text = "#404040"
+# The basic 16 colors
+# black
+palette = 0=#404040
+palette = 8=#625A5B
+# red
+palette = 1=#E3716E
+palette = 9=#EC8685
+# green
+palette = 2=#819B69
+palette = 10=#8BAE68
+# yellow
+palette = 3=#B77E64
+palette = 11=#D68C67
+# blue
+palette = 4=#6099C0
+palette = 12=#61ABDA
+# magenta
+palette = 5=#B279A7
+palette = 13=#CF86C1
+# cyan
+palette = 6=#66A5AD
+palette = 14=#65B8C1
+# white
+palette = 7=#F0E4CF
+palette = 15=#C0AB86