Typescript ES6 support

[victors1682]

Describe the feature you'd like I attempted to iterate through a map using ES6 syntax but had to resort to the older approach. Not urgent but nice to have.

error TS2802: Type 'Map<any, any>' can only be iterated through when using the '--downlevelIteration' flag or with a '--target' of 'es2015' or higher.

     for (let [key, values] of variantMap) {

https://github.com/vtex/faststore/blob/271888ce74d9ca8ea683ec299f90c6aeff27f26f/packages/core/tsconfig.json#L23

[gvc]

Thank you for the feedback. The team will look into this 🚀