feat: Include Confirmation dialogue if a file is about to be overwritten

- Added in a `huh.NewConfirm` and `huh.NewInput` fields, that checks
  if the output file already exists within the given directory
- If the user selects to `overwrite` the file, execution continues as is
- If the user selects to `not overwrite` the file, an `input` field is
  provided to select a new output filename

main.go

@@ -17,6 +17,7 @@ import (
 	"github.com/beevik/etree"
 	in "github.com/charmbracelet/freeze/input"
 	"github.com/charmbracelet/freeze/svg"
+	"github.com/charmbracelet/huh"
 	"github.com/charmbracelet/lipgloss"
 	"github.com/charmbracelet/log"
 	"github.com/charmbracelet/x/exp/term/ansi"
@@ -133,6 +134,34 @@ func main() {
 		config.Output = defaultOutputFilename
 	}
 
+	// Check if file already exists
+	if _, err := os.Stat(config.Output); err == nil {
+		var confirm bool
+		var newOutputFilename string
+
+		confirmOverwriteForm :=
+			huh.NewConfirm().
+				Title(fmt.Sprintf("'%s' already exists. Would you like to overwrite this file?", config.Output)).
+				Value(&confirm)
+
+		newOutputFileNameForm := huh.NewInput().
+			Title("Enter new output filename to use").
+			Value(&newOutputFilename)
+
+		err = confirmOverwriteForm.Run()
+		if err != nil {
+			printErrorFatal("could not retrive overwrite confirmation", err)
+		}
+
+		if !confirm {
+			err := newOutputFileNameForm.Run()
+			if err != nil {
+				printErrorFatal("could not retrieve new output filename to use", err)
+			}
+			config.Output = newOutputFilename
+		}
+	}
+
 	scale = 1
 	if autoHeight && autoWidth && strings.HasSuffix(config.Output, ".png") {
 		scale = 4