Improve image zooming (scroll wheel)

[starypatyk]

I propose a few small changes to the image zooming code that should improve UX in this area:

1. f854d9d - this fixes calculation of the displayed image dimensions - currently the .modal-container element does not include the header, so the calculation should not compensate for this. After this change the same image location stays under the mouse cursor position when zooming in/out. Previously the position drifted away slightly.
2. c6f34c8 - this enables zooming beyond natural image dimensions (up to 500% of the default view - apparently as originally intended). Changing maxHeight/maxWidth over 100% does not enlarge the image, so I had to switch to height/width. This in turn required switching animations off - it looked very ugly with the animations on. The animations did not work previously, so it seems a fair trade-off for me. 😉 I have also made a few cosmetic changes to simplify calculations.
3. ee0c498 - I have changed the zoomRatio calculations to always increase/decrease it by 10% (rather than linearly). This feels more natural - esp. with larger zoom levels.

When zooming beyond 100% this still uses the preview image - so obviously there will be some blurriness. Requesting the original image in this case would certainly be a better solution, but it seems to be something for a separate PR.

PS. As a follow-up, I plan to work on pinch to zoom on mobile devices (#917)

Edit I see that all cypress tests failed. 😞 This seems to be unrelated to this PR.

[skjnldsv]

Works great! Thank you so much @starypatyk !!! 🙇 🙏

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