expose an option of the Map: zoom in/out button

Map({
enableControlPanel: true,
})

So we got the zoom in/out button on the bottom right corner.

leaflet already has this feature, so we just need to expose it.

---

Some hints:

- Please read our [readme](https://github.com/Greenstand/treetracker-web-map-core#treetracker-web-map-core) for more information/guide/tutorial.
- Here is [an engineering book](https://greenstand.gitbook.io/engineering/) in Greenstand.
- To know more about our organization, visit our [website](https://greenstand.org).
- If you want to join the slack community (some resources need the community member's permission), please leave your email address.

Start with the repository README and the Map({ enableControlPanel: true }) entry point, then inspect how the existing control panel is exposed. Use Leaflet's zoom control documentation as the reference. Done means callers can opt into the zoom in/out buttons and the buttons appear in the map as described.

Written by the indexing model from the issue text.