1.21.1 nf crawl fix

[XM666-Dev]

Hello, I would like to ask whether it would be possible to add a transition to the Crawl animation (which relies on the vanilla swimAmount animation).

SlidingAnimator already implements a proper end transition, so it seems reasonable for Crawl to have a similar treatment.

Currently, in PlayerRenderer, the vanilla game applies a fixed positional offset when the player is swimming. This results in some visual inconsistencies, especially when transitioning in or out of the crawl state.

In this PR, the issue is addressed by interpolating the offset value instead of applying it abruptly. An additional offset is applied dynamically to smooth the swimAmount transition.

After this fix:

I am not entirely certain whether this adjustment belongs in this mod, but since Crawl progression consistently depends on this behavior, it seems necessary to refine it here.

[alRex-U]

Basically ParCool doesn't fix vanilla features so I'm wondering whether we should do this.
Is this possible to apply this change by CrawlAnimator( or only when CrawlAnimator is working)