Add @api stable annotations to ol.layer.Base
Add @api stable annotations to ol.layer.Layer
Add @api stable annotations to ol.layer.Group
Add @api stable annotations to ol.layer.Image
Add @api stable annotations to ol.layer.Tile
Add @api stable annotations to ol.layer.Vector
Add @api annotations to ol.layer.Tile
Add docs for the tile layer preload option
Merge pull request #2552 from elemoine/apistable

Add @api stable annotations for the ol.layer namespace