Clearer guidance on adding multiple layers

[kitmacleod]

Great work Tim et al with OL and this important learning resource (esp. since exising OL3 books are becoming less useful).

Please consider that there maybe a need for clearer guidance on how to add multiple layers to a map object. From my limited OL experience, I think there are at least four ways that this is done in existing resources (various books, OL examples, workshop, API docs etc). As a new OL user I find this confusing.

My suggestion is that you include how to add multiple layers in the workshop examples/code. I appreciate there may be different use cases for adding layers in different ways. I also appreciate there are multiple types of layers.

[ThomasG77]

@kitmacleod I'm not sure it should be in the workshop but to answer https://medium.com/@ThomasG77/multiple-ways-to-add-layers-in-openlayers-2c9569beb948 . Feel free to comment on the blog post side to avoid polluting the tracker ;) as I already do answering you...