TUN-3201: Create base cloudflared UI structure

vendor/github.com/rivo/tview/README.md

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+# Rich Interactive Widgets for Terminal UIs
+
+[![Godoc Reference](https://img.shields.io/badge/godoc-reference-blue.svg)](https://pkg.go.dev/github.com/rivo/tview)
+[![Go Report](https://img.shields.io/badge/go%20report-A%2B-brightgreen.svg)](https://goreportcard.com/report/github.com/rivo/tview)
+
+This Go package provides commonly needed components for terminal based user interfaces.
+
+![Screenshot](tview.gif)
+
+Among these components are:
+
+- __Input forms__ (include __input/password fields__, __drop-down selections__, __checkboxes__, and __buttons__)
+- Navigable multi-color __text views__
+- Sophisticated navigable __table views__
+- Flexible __tree views__
+- Selectable __lists__
+- __Grid__, __Flexbox__ and __page layouts__
+- Modal __message windows__
+- An __application__ wrapper
+
+They come with lots of customization options and can be easily extended to fit your needs.
+
+## Installation
+
+```bash
+go get github.com/rivo/tview
+```
+
+## Hello World
+
+This basic example creates a box titled "Hello, World!" and displays it in your terminal:
+
+```go
+package main
+
+import (
+	"github.com/rivo/tview"
+)
+
+func main() {
+	box := tview.NewBox().SetBorder(true).SetTitle("Hello, world!")
+	if err := tview.NewApplication().SetRoot(box, true).Run(); err != nil {
+		panic(err)
+	}
+}
+```
+
+Check out the [GitHub Wiki](https://github.com/rivo/tview/wiki) for more examples along with screenshots. Or try the examples in the "demos" subdirectory.
+
+For a presentation highlighting this package, compile and run the program found in the "demos/presentation" subdirectory.
+
+## Documentation
+
+Refer to https://pkg.go.dev/github.com/rivo/tview for the package's documentation.
+
+## Dependencies
+
+This package is based on [github.com/gdamore/tcell](https://github.com/gdamore/tcell) (and its dependencies) as well as on [github.com/rivo/uniseg](https://github.com/rivo/uniseg).
+
+## Your Feedback
+
+Add your issue here on GitHub. Feel free to get in touch if you have any questions.