feat: Add gum spin command

Spin provides a shell script interface for the spinner bubble. It is
useful for displaying that some task is running in the background while
consuming it's output so that it is not shown to the user.

For example, let's do a long running task:
```
sleep 5
```

We can simply prepend a spinner to this task to show it to the user,
while performing the task / command in the background.

```
gum spin -t "Taking a nap..." -- sleep 5
```

The spinner will automatically exit when the task is complete.

spin/command.go

@@ -0,0 +1,22 @@
+package spin
+
+import (
+	"github.com/charmbracelet/bubbles/spinner"
+	tea "github.com/charmbracelet/bubbletea"
+	"github.com/charmbracelet/lipgloss"
+)
+
+// Run provides a shell script interface for the spinner bubble.
+// https://github.com/charmbracelet/bubbles/spinner
+func (o Options) Run() {
+	s := spinner.New()
+	s.Style = lipgloss.NewStyle().Foreground(lipgloss.Color(o.Color))
+	s.Spinner = spinnerMap[o.Spinner]
+	m := model{
+		spinner: s,
+		title:   o.Title,
+		command: o.Command,
+	}
+	p := tea.NewProgram(m)
+	_ = p.Start()
+}

spin/options.go

@@ -0,0 +1,10 @@
+package spin
+
+// Options is the customization options for the spin command.
+type Options struct {
+	Command []string `arg:"" help:"Command to run"`
+
+	Color   string `help:"Spinner color" default:"#FF06B7"`
+	Title   string `help:"Text to display to user while spinning" default:"Loading..."`
+	Spinner string `help:"Spinner type" type:"spinner" enum:"line,dot,minidot,jump,pulse,points,globe,moon,monkey,meter,hamburger" default:"dot"`
+}

spin/spin.go

@@ -0,0 +1,51 @@
+package spin
+
+import (
+	"os/exec"
+
+	"github.com/charmbracelet/bubbles/spinner"
+	tea "github.com/charmbracelet/bubbletea"
+)
+
+type model struct {
+	spinner spinner.Model
+	title   string
+	command []string
+}
+
+type finishCommandMsg struct{ output string }
+
+func commandStart(command []string) tea.Cmd {
+	return func() tea.Msg {
+		var args []string
+		if len(command) > 1 {
+			args = command[1:]
+		}
+		out, _ := exec.Command(command[0], args...).Output()
+		return finishCommandMsg{output: string(out)}
+	}
+}
+
+func (m model) Init() tea.Cmd {
+	return tea.Batch(
+		m.spinner.Tick,
+		commandStart(m.command),
+	)
+}
+func (m model) View() string { return m.spinner.View() + " " + m.title }
+
+func (m model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
+	var cmd tea.Cmd
+	switch msg := msg.(type) {
+	case finishCommandMsg:
+		return m, tea.Quit
+	case tea.KeyMsg:
+		switch msg.String() {
+		case "ctrl+c":
+			return m, tea.Quit
+		}
+	}
+
+	m.spinner, cmd = m.spinner.Update(msg)
+	return m, cmd
+}

spin/spinners.go

@@ -0,0 +1,17 @@
+package spin
+
+import "github.com/charmbracelet/bubbles/spinner"
+
+var spinnerMap = map[string]spinner.Spinner{
+	"line":      spinner.Line,
+	"dot":       spinner.Dot,
+	"minidot":   spinner.MiniDot,
+	"jump":      spinner.Jump,
+	"pulse":     spinner.Pulse,
+	"points":    spinner.Points,
+	"globe":     spinner.Globe,
+	"moon":      spinner.Moon,
+	"monkey":    spinner.Monkey,
+	"meter":     spinner.Meter,
+	"hamburger": spinner.Hamburger,
+}