Add support for decorate resty.Request

[lexcao]

Is your feature request related to a problem? Please describe.
I want to add custom headers per the request.

Describe the solution you'd like
Support options, then we could add options...Options for every method without breaking existing API

type Options func(*resty.Request)
// GetRequestWithBearerAuth returns a JSON base request configured with an auth token.
func (g *GoCloak) GetRequestWithBearerAuth(ctx context.Context, token string, options...Options) *resty.Request {
	request := g.GetRequest(ctx).
		SetAuthToken(token).
		SetHeader("Content-Type", "application/json")

	for _, option := range options {
		option(request)
	}

	return request
}

// the API may look like this
func (g *GoCloak) Login(ctx context.Context, clientID, clientSecret, realm, username, password string, options...Options) (*JWT, error)

Describe alternatives you've considered
I know there is SetPreRequestHook existed in RestyClient, but it could not be set for a single specific request.

Additional context
I am willing to help.