Add Cairn gear packages

[fjallnari]

Add https://cairnrpg.com/cairn-srd/#optional-gear-packages as ItemCairn arrays
to allow for more flexible character generation.

[fjallnari]

Refactoring Cairn items like armors #88, would allow for us to save Gear packages using something like this:

export const GEAR_PACKAGES = {
    cleric: [
        WEAPONS['War Hammer'],
        ARMORS['Chainmail'],
        ARMORS['Gauntlets'],
        ... createWeapon('Cleansing Blade', 'd6') // can be used for custom non-SRD items, which are not repeated elsewhere
        ... createItem('Holy Symbol (Ward once per day)'),
        ... createItem('Cloak of the Order')
    ]
}

[ptaranat]

I have a preference for the following:

const createItem = ({ name, description, bulky, stacks }: {
    name: string,
    description?: string,
    bulky?: boolean,
    stacks?: boolean,
}
): ItemCairn => {
    return { name: name, type: 'item', description: description, bulky, stacks: stacks, };
}

This allows createItem({ name: "Dice Set", stacks: true }) instead of createItem("Dice Set", "", false, true).

We could also import GEARS, TOOLS, and TRINKETS under ITEMS, so that we can add createItem in one file.

[fjallnari]

I like the createItem function, and we can for sure merge the TOOLS etc. under one file. However, I've noticed a flaw in my approach. If we use createArmor the way it works now, the resulting gear package would be inconsistent if we add it from the SRD items vs. if we create it from scratch.

cleric: [
    WEAPONS["War Hammer"],
    createWeapon("Cleansing Blade", "d6"),
]

results in this:

cleric: [
  {
    name: 'War Hammer (d10, bulky)',
    type: 'weapon',
    bulky: true,
    damage: 'd10'
  },
  { 'Cleansing Blade': [Object] },

I think it would be best if we just used simple classes for armor and weapons, like so:

export class ArmorCairn {
    public record: Record<string, Partial<ItemCairn>>;

    constructor ({ name, armor, bulky }: { name: string, armor: string, bulky?: boolean }) {
        const prettyName = `${name} (${armor} Armor${bulky ? ', bulky': ''})`;
        this.record = {[name]: { name: prettyName, type: 'armor', bulky, armor: armor }};
        return this;
    }

    public getItem() {
        return this.record[Object.keys(this.record)[0]];
    }
}

Then we can use e.g. ... new ArmorCairn({ name: 'Shield', armor: '+1' }).record to generate the SRD armors, and new ArmorCairn({ name: 'Shield', armor: '+1' }).getItem() to create custom armor.