Add support for commas in ItemStacks

[object-Object]

https://vazkiimods.github.io/Patchouli/docs/patchouli-advanced/itemstack-format

This is used for spotlight pages at least, possibly elsewhere too?

https://github.com/VazkiiMods/Patchouli/blob/1.21.1/Xplat/src/main/java/vazkii/patchouli/client/book/template/variable/ItemStackArrayVariableSerializer.java

https://github.com/VazkiiMods/Patchouli/blob/1.21.x/Xplat/src/main/java/vazkii/patchouli/common/util/ItemStackUtil.java#L141