Assess if the `ExplorationLayer` should be removed

## Description

Clarify if the `ExplorationLayer` should indeed be removed or not, see [src/index.ts](https://github.com/equinor/videx-map/tree/master/src/index.ts)

## Acceptance criteria

- If the removal is no longer on the agenda
- remove the comment
- update documentation & README accordingly
- If the removal is needed
- do the clean-up as part of this user story if the scope is less than ~ 2 days. if more work is needed, please create a follow-up user story

Start by reading the ExplorationLayer reference and comment in src/index.ts, then inspect the related documentation and README. Determine whether removal is still planned; if not, remove the comment and update the documentation, or assess the cleanup scope and create a follow-up user story if it exceeds about two days.

Written by the indexing model from the issue text.