Typing for ImageryLayer contructor is incorrect

[angrycat9000]

JSDoc indicates both the provider and options arguments are required.

cesium/packages/engine/Source/Scene/ImageryLayer.js

Lines 135 to 136 in 003922b

	* @param {ImageryProvider} imageryProvider The imagery provider to use.
	* @param {ImageryLayer.ConstructorOptions} options An object describing initialization options

However they are both defaulted to the empty object in the constructor. Though imageryProvider has already been assigned to this._imageryProvider at this points so not sure if that is a bug or this should truly be an required argument.

cesium/packages/engine/Source/Scene/ImageryLayer.js

Lines 165 to 166 in 003922b

	options = defaultValue(options, defaultValue.EMPTY_OBJECT);
	imageryProvider = defaultValue(imageryProvider, defaultValue.EMPTY_OBJECT);

This causes errors with Typescript when the options argument is not provided