[FEATURE] add more basemap styles to geohub

[JinIgarashi]

Feature Description

We maybe can borrow some style codes from OpenMapTiles

https://openmaptiles.org/styles/

For example,

Dark style, Fiord color, tonor style

they look good for visualisation with datasets

Feature Implementation

our style repo

https://github.com/UNDP-Data/style

Feature Alternatives

No response

Feature Impact

No response

Feature Rationale

No response

Feature Considerations

No response

Feature Requirements

No response

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