Component | LeafletMap: Configurable inner label color

[rokotyan]

This PR adds support for central labels color #155

• Adding pointLabelColor and clusterLabelColor config properties;
• Adding new CSS variables:

    --vis-map-cluster-inner-label-text-color-dark: #5b5f6d;
    --vis-map-cluster-inner-label-text-color-light: #fff;

    --vis-map-point-inner-label-text-color-dark: #5b5f6d;
    --vis-map-point-inner-label-text-color-light: #fff;

    --vis-map-point-bottom-label-text-color: #5b5f6d;

• Updated Angular wrapper;
• New dev app example:
• Updated docs:

[rokotyan]

@reb-dev This is ready for review

[reb-dev]

Nice, looks good.