Explanation of steps in the GIF

The first thing is to reduce the timeline space in order to get it zoomed enough to work in a span of 1 second.

Second, bring the timeline cursor to the beginning so that our first frame starts at zeroth second.

Press shift, click and hold the little red square affixed with your picture, and very slightly drag it outside or inside. As soon as you move it slightly, you will find a rhombus keyframe added in the timeline. This shows that your animation will start with this image size. Release the click-hold and the shift button now.

You can jump to the code repo any time you want!

Move the timeline cursor a few milliseconds ahead of the start. This is the place where your image will zoom in bigger. Now, do the same thing, press and hold shift, click and hold the little red square and drag it outside and the image will start to expand.

Expand the image as much as you would like to. This will also create a new keyframe on the timeline. Now copy this keyframe and paste it a few milliseconds further on the timeline. We did this so that our image expands and stays expanded for a few milliseconds in order to create an inertia effect.

Now copy the first zeroth time keyframe and paste it at the end of the timeline as shown in the GIF. This is because we want our image to come back to its original state at the end.