Miscellaneous changes for `v0.4.0`

[josxha]

• turn async methods sync
• remove *Sync method overloads
• create *Async method overloads for webview platforms
• static typed initStyle parameter
• deintegrate cocoapods
• add typed layer properties with expression support to style layers
• remove deprecations
• android: request location permissions on activation of the location marker to match the iOS behavior (or replace with a dart implementation of the location marker)
• Use LngLatQuad for VideoSource.coordinates, just like ImageSource
• Look again into enhancing the test situation on android + ios
• create v0.4 docs
• initZoomLevel, etc. should be nullable and pick the style default if not set -> use initCamera instead?
• only export geobase classes that are used in the public api
• add .devcontainer/devcontainer.json
• add vscode code workspace
• add style.layers['id'] and style.layers
• add style.sources['id'] and style.sources
• ...