#4 Add package builder

[thekingofcity]

This requires #5 to be merged.

Currently, I update id for every city name like shanghai to CityCode.Shanghai in city-config.ts. This is a hardcoded replace. Since shanghai is still valid as long as we have enum CityCode, I'm wondering about this replacement process.

json:
    {
        "id": "shanghai",
        "country": "CN",
        "name": {
            "en": "Shanghai",
            "zh": "上海"
        }
    },

ts option1:
  {
    id: CityCode.Shanghai,
    country: 'CN',
    name: { en: 'Shanghai', zh: '上海' }
  },

ts option2:
  {
    id: 'shanghai',
    country: 'CN',
    name: { en: 'Shanghai', zh: '上海' }
  },

---

$ node --loader ts-node/esm .\builder\build.ts

A successful build will be

\RMG-PALETTE\BUILDER
│  build.ts
│  city-config.ts
│  constants.ts
│  
└─palettes
        baku.ts
        barcelona.ts
        beijing.ts
        cairo.ts
        changsha.ts
        chengdu.ts
        chongqing.ts
        dalian.ts
        delhi.ts
        dongguan.ts
        dortmund.ts
        edinburgh.ts
        foshan.ts
        glasgow.ts
        guangzhou.ts
        hangzhou.ts
        harbin.ts
        hongkong.ts
        istanbul.ts
        kansai.ts
        kaohsiung.ts
        klangvalley.ts
        london.ts
        macao.ts
        madrid.ts
        nanjing.ts
        newtaipei.ts
        osaka.ts
        oslo.ts
        other.ts
        paris.ts
        qingdao.ts
        sanfrancisco.ts
        sanktpeterburg.ts
        santiago.ts
        saopaulo.ts
        seoul.ts
        shanghai.ts
        shenzhen.ts
        singapore.ts
        stockholm.ts
        suzhou.ts
        taipei.ts
        tehran.ts
        tianjin.ts
        tokyo.ts
        toronto.ts
        tyneandwear.ts
        wuxi.ts
        xiamen.ts
        xian.ts