fix(balance): kilnable heavy bones

[Goredell]

Purpose of change

While it's possible to craft charcoal from heavy bones using craft recipies, kiln does not allow to put those inside. This one fixes it.

Describe the solution

Add "bone_heavy" to method that handles kilns.

Testing

Try putting heavies in, lit kiln, check result.

Checklist

Mandatory

• I wrote the PR title in conventional commit format.
• I ran the code formatter.
• I linked any relevant issues using github keyword syntax like closes #1234 in Summary of the PR so it can be closed automatically.
• I've committed my changes to new branch that isn't main so it won't cause conflict when updating main branch later.

[chaosvolt]