func WithTemplatesFromFiles(ts map[string][]string) Option {
	return func(o *Options) {
		for name, files := range ts {
			o.files[name] = files
		}
	}
}
func WithTemplatesFromFiles(ts map[string][]string) Option {
	return func(o *Options) {
		for name, files := range ts {
			o.files[name] = files
		}
	}
}
// WithTemplatesFromFiles adds a map of templates parsed from files.