Support for format expression vertical-align property

[stanislawpuda-tomtom]

Is your feature request related to a problem? Please describe.
maplibre-style-spec issue
maplibre-gl-js PR

This is about to introduces support for vertical-align property in format expression.

Implementation should follow maplibre-gl-js.

Describe the solution you'd like

vertical-align property in format expression enables to specify how each section should be positioned in relation to biggest element in line. There are three possible options:

• "bottom" default: text baseline or image bottom are in line - this is current behaviour.
• "center": image center or text center are in line.
• "top": image top and text top are in

Describe alternatives you've considered

An HTML layer for maplibre-gl-js (or equivalent for other renderers) was considered, but was dropped due to:

• performance limitation
• lack of label collision support
• more difficult to use
• not multi-platform