Create/store suite of BGC future maps

The script `R/04_CreateBGCfutsMap.R` was copied from `modules/BC_HexGrid/Create_BCMap.R` as a placeholder for (potential) v2.0 tasks that this script would enable accomplishing:

- Creating a set of maps of "BGC futures" (e.g. dry-hot, dry-moist) that are hosted on the server
- Creating maps of "requested" "BGC futures"

Start by comparing R/04_CreateBGCfutsMap.R with modules/BC_HexGrid/Create_BCMap.R to understand the placeholder workflow. Define the required set of BGC futures maps, including dry-hot and dry-moist examples, and the requested BGC futures maps, then determine how they should be hosted on the server. Done means the scripts create and store the agreed map sets.

Written by the indexing model from the issue text.