Add filled tonal button style

[kafri8889]

Any plan to add filled tonal button style?

/**
 * Available button styles.
 */
enum class ButtonStyle {

    /**
     * Text button.
     */
    TEXT,

    /**
     * Elevated button.
     */
    ELEVATED,

    /**
     * Filled button.
     */
    FILLED,

    /**
     * Outlined button.
     */
    OUTLINED
}