add cooperativeGestures option

[RoduanKD]

Peace be upon you guys! I hope you're doing well. I've added support to cooperative gestures, enabling zoom scrolling only when holding ctrl/command key. sample usage:

<mgl-map
    id="map"
    :access-token="accessToken"
    :map-style="style"
    :cooperative-gestures="true"
    @load="onMapLoad"
/>

screenshot:

incase someone needed this feature before this pull is merged you can use it by installing the package from this pull request directly: npm i soal/vue-mapbox#pull/258/head

have a nice day. thanks