feat(plugin): replaceplaceholder dashboard header with stylized ASCII art

Added a new decorative multi‑line ASCII header to the dashboard preset, enhancing visual appeal.

- New Features  - Introduced multi‑line ASCII art header with improved typography
- Enhancements
  - Replaced plain placeholder with eye‑catching design
- Bug Fixes
  - (none)

plugin/snacks.lua

@@ -65,10 +65,13 @@ Snacks.setup({
     dashboard = {
         preset = {
             header = [[
-░█░█░█▀▀░█░█░█▀▀░█▀█░█▀▄░█▀▀░█░█
-░█▀▄░█▀▀░░█░░█░░░█░█░█░█░█▀▀░▄▀▄
-░▀░▀░▀▀▀░░▀░░▀▀▀░▀▀▀░▀▀░░▀▀▀░▀░▀
-                            ]],
+ ██╗  ██╗███████╗██╗   ██╗ ██████╗ ██████╗ ██████╗ ███████╗██╗  ██╗
+ ██║ ██╔╝██╔════╝╚██╗ ██╔╝██╔════╝██╔═══██╗██╔══██╗██╔════╝╚██╗██╔╝
+ █████╔╝ █████╗   ╚████╔╝ ██║     ██║   ██║██║  ██║█████╗   ╚███╔╝ 
+ ██╔═██╗ ██╔══╝    ╚██╔╝  ██║     ██║   ██║██║  ██║██╔══╝   ██╔██╗ 
+ ██║  ██╗███████╗   ██║   ╚██████╗╚██████╔╝██████╔╝███████╗██╔╝ ██╗
+ ╚═╝  ╚═╝╚══════╝   ╚═╝    ╚═════╝ ╚═════╝ ╚═════╝ ╚══════╝╚═╝  ╚═╝
+            ]],
         },
         sections = {
             { section = 'header' },