Custom fins don't have a crafting recipe

### Describe the bug

The crafting recipe added by the diving rework #68296 dont have a crafting recipe. The normal diving fins do, they are fine, just the ones you attach to your wetsuit boots don't.
Or I screwed up in searching for them, but since the original PR doesn't have a recipe for them and I didn't see anything new about it or in the game files, I doubt that.

### Attach save file

Save file won't help

### Steps to reproduce

Search the game files for swim_fins_custom
Find only the item definition

### Expected behavior

Very easy to add a recipe, maybe raise the learned recipe compared to the basic fins since they are custom and you need to figure out how exactly to make them fit the boot and help you. Maybe just by one level since it shouldn't be that hard.
Or sync it with the boot requirement since until then the recipe would be useless. This might be the best solution.

### Screenshots

_No response_

### Versions and configuration

- OS: Windows
- OS Version: 10.0.19045.3693 (22H2)
- Game Version: ee51225 [64-bit]
- Graphics Version: Tiles
- Game Language: System language []
- Mods loaded: [
Dark Days Ahead [dda],
Disable NPC Needs [no_npc_food],
Slowdown Fungal Growth [no_fungal_growth],
Xedra Evolved [xedra_evolved],
sees-player, run, crouch, bleed icons, retrodays [sees_player_retro],
Bombastic Perks [bombastic_perks],
Stats Through Kills [stats_through_kills]
]

### Additional context

This is an easy fix, so first time contributors can take a swing at it. If nobody touches it I'll add it when I have a night shift and don't forget my laptop. Or if I decide to go diving in-game, but That's not happening anytime soon

Search the game files for swim_fins_custom and compare its item definition with the normal diving fins and their crafting recipe. Determine the appropriate learned-skill or boot-requirement level from those related definitions, add the missing recipe, and verify that the custom fins can then be crafted in-game.

Written by the indexing model from the issue text.