feat(display): add methods to display

- Add `indent`, `faint`, and `underline` methods to `display`
- Add tests for the above

internal/display/faint.go

@@ -0,0 +1,8 @@
+package display
+
+import "fmt"
+
+// Faint returns an faint string
+func Faint(str string) string {
+	return fmt.Sprintf(fmt.Sprintf("\033[2m%s\033[0m", str))
+}