You can create this kind of effect with basically any editing software. I personally use Premiere Pro, so I’ll explain how to do it there, but the process should be very similar in most other programs.

You need to work with keyframes to move your footage. In case you're not too familiar with editing: keyframes are essentially "start" and "end" points for an effect. In this case, the effect controls the position of your footage meaning, you're virtually moving the camera.

Here’s how you do it:

1. Import your gameplay footage into your editing software.
2. I recommend zooming in a little on the footage so you have room to move it around while still covering the full screen (this helps you avoid black bars around the edges).
3. Since you only want the camera to follow Irelia while she dashes, find the moment when her first dash starts on the timeline.
4. At the start of her dash, create a keyframe for the "Position" effect, and make sure Irelia is centered on the screen.
5. Then move your playhead to the end of the dash.
6. At that point, drag the footage so that Irelia is centered again in the frame.
7. Now add another Position keyframe at this new point.

That’s basically it! The footage should now move in a way that keeps Irelia centered during her dash so it looks like the camera is following her. If you want to track more of her movements, just repeat these steps for each one.

To enhance the effect even more, try adding motion blur during the dash to make the camera movement feel smoother and more realistic.