feat(style): trim line spaces (#767)

Lipgloss applies aligning on the string as given to it, and ascii art
usually contain left whitespaces to align things.

This adds an option to trim space on all lines of the input, before
giving it to lipgloss, so aligning use only non-whitespace content.

style/ascii_a.txt

@@ -0,0 +1,7 @@
+   #
+  # #
+ #   #
+#     #
+#######
+#     #
+#     #

style/command.go

@@ -25,6 +25,13 @@ func (o Options) Run() error {
 			return errors.New("no input provided, see `gum style --help`")
 		}
 	}
+	if o.Trim {
+		var lines []string
+		for _, line := range strings.Split(text, "\n") {
+			lines = append(lines, strings.TrimSpace(line))
+		}
+		text = strings.Join(lines, "\n")
+	}
 	fmt.Println(o.Style.ToLipgloss().Render(text))
 	return nil
 }

style/options.go

@@ -3,6 +3,7 @@ package style
 // Options is the customization options for the style command.
 type Options struct {
 	Text  []string        `arg:"" optional:"" help:"Text to which to apply the style"`
+	Trim  bool            `help:"Trim whitespaces on every input line" default:"false"`
 	Style StylesNotHidden `embed:""`
 }