WIP: Upgrade to JS modules, TypeScript and LitElement

[justinfagnani]

Just starting the work, PR to track for now.

I'm changing the API a bit, trying to make it simpler and closer to the Maps API:

• Properties that mirror Maps API options are named closer to the Maps API
• Removed the separate markers and object slots
• Always forward all Maps events as DOM events, remove the attribute that control forwarding
• Rename some properties to be longer and clearer (info → infoWindow, version → apiVersion, etc)
• Removed clear() which removed the Maps marker object, but not the <google-map-marker> DOM nodes. Just remove the nodes instead.

I'm thinking about removing <google-map-point> and using a path property on <google-map-poly> instead. <google-map-poly> should probably be replaced with <google-map-polyline>, <google-map-polygon>, <google-map-rectangle>, <google-map-circle>, etc.

[ghost]

Why this branch has not been merged yet (almost 2 years and every check seems ok)?

Ok, I understand that some properties has changed, but, by upgrading the major version, it should not break every projects that use it.

Do you need something special before merging it?
Maybe some documentation or unit tests, I don't know.

I don't want to fork it because I think it could be useful for a lot of people to have a typescript/litelement version of this web-component