How to give player a "dash" ability?

I'm making a 2D isometric/top down kind of game.
My character has this movement script attached:

public class PlayerController : MonoBehaviour {

 public float moveSpeed = 5f;
 public Vector2 lastMove;

 private Rigidbody2D myRigidbody;

 public bool canMoove; //used by scripts to halt player movement

 void Start () {
     myRigidbody = GetComponent <Rigidbody2D> ();
     canMoove = true;
 }
 
 void FixedUpdate () {

     if (canMoove == true) {
         if (Input.GetAxisRaw ("Horizontal") > 0.5f || Input.GetAxisRaw("Horizontal") < -0.5f) {

             myRigidbody.velocity = new Vector2 (Input.GetAxisRaw ("Horizontal") * moveSpeed, myRigidbody.velocity.y);
             playerMoving = true;
             lastMove = new Vector2 (Input.GetAxisRaw ("Horizontal"), 0f);
         } //movement on the horizontal axis

         if (Input.GetAxisRaw ("Vertical") > 0.5f || Input.GetAxisRaw("Vertical") < -0.5f) {

             myRigidbody.velocity = new Vector2 (myRigidbody.velocity.x, Input.GetAxisRaw ("Vertical") * moveSpeed);
             playerMoving = true;
             lastMove = new Vector2 (0f, Input.GetAxisRaw ("Vertical"));
         } //movement on the vertical axis

         if(Input.GetAxisRaw ("Horizontal") < 0.5f && (Input.GetAxisRaw ("Horizontal") > -0.5f))
         {
             myRigidbody.velocity = new Vector2 (0f, myRigidbody.velocity.y);
         } //stops ice movement effect

         if (Input.GetAxisRaw ("Vertical") < 0.5f && Input.GetAxisRaw("Vertical") > -0.5f)
         {
             myRigidbody.velocity = new Vector2 (myRigidbody.velocity.x, 0f);
         } //stops ice movement effect
     } else {
         myRigidbody.velocity = new Vector2 (0f, 0f);
     }
 }  

I would like to give the player a "dash" ability similar to those in Hollow Knight and Hyper Light Drifter. Where while moving, the character dashes forward in the direction they're moving (including along the diagonal). Or if they aren't moving, they just dash in the direction that they're facing.

Any ideas about how I could go about this? I've tried several scripts but none of them allow for a diagonal dash - only strictly horizontal and vertical. Any help would be appreciated.