feat: set proper inputbox limit (pr/issue)

On GitHub, (almost) all text content supplied through their API is limited by 65536 characters. Before this commit, the limit for all textboxes in gh-dash was 400 characters.
While it is possible to set this field (CharLimit) to unlimited (-1), 65536 seems like a sensible default.

Closes: #517
See: https://github.com/orgs/community/discussions/27190

Author: 25huizengek1

ui/components/inputbox/inputbox.go

@@ -28,6 +28,7 @@ func NewModel(ctx *context.ProgramContext) Model {
 	ta := textarea.New()
 	ta.ShowLineNumbers = true
 	ta.Prompt = ""
+        ta.CharLimit = 65536
 	ta.FocusedStyle.Base = lipgloss.NewStyle()
 	ta.FocusedStyle.CursorLine = lipgloss.NewStyle().
 		Background(ctx.Theme.FaintBorder).