Add i3s parser and example

[xintongxia]

// steps to start the application
yarn bootstrap // or npm run bootstrap, only need do once

cd examples/i3s/deck.gl
yarn 
yarn start-local

[coveralls]

Coverage decreased (-2.5%) to 53.438% when pulling 67c1698 on xx/i3s into 7cbfdab on master.

[ibgreen]

Fix description

[xintongxia]

@Tamrat-B

I updated with your code changes plus some fixes.

Performance is improved and the LoD looks correct to me.

Next work:

• zoom in and zoom out for a couple of times, the tiles do not update as expected, parts of tiles are missing.
• Should enable caching for tiles and invalidate based on tile priority

We can sync up if you have time. I'll continue to debug the issues.

[Tamrat-B]

@xintongxia sounds good! I'm traveling the next few days but we can find time to sync up early next week. I'll ping you. The prioritization list looks good too. One that might be good to add to the list would be compressed texture support - as you can see after few minutes of usage mem usage just keeps on growing and results in a crash (perhaps might be good also to visit the tile unloading strategy ?); Using compressed textures should dramatically reduce mem consumption. I also think it will be good to introduce an LOD bias control (fudge factor) to the Lod selection criteria - to allow us to experiment different LOD quality settings - i can send you changes for that as well.