Improve the starting notification to use helper.echo from denops_std and make it optionally

[peacock0803sz]

Motivation and Context

The current implementation uses console.log with default Deno.serve to show server startup notifications.
This results in red-colored output (tested in light-based terminals), and doesn't align well with denops's best practices.

What Changed

1. Changed the server startup notification to use helper.echo from denops_std instead of Deno.serve's default logging
2. Added a new option g:glance#server_silent that allows users to:
   • Completely suppress the startup notification when set to true
   • Maintain the default notification behavior when set to false (or not set)

Demo Videos

Current Behavior

vim-glance-asis.mp4

Default Behavior with this PR

vim-glance-noslient.mp4

Completely Silenced

vim-glance-slient.mp4

I hope this PR makes vim-glance more gently (for your eyes 😆 )

[peacock0803sz]

TODOs

• Update description for this PR
• Add demo screenshots

[tani]

Thank you so much!