Module provides `Style` function that can be used to construct content style modification via stylesheet files or CSS rules. @class @constructor The Style constructor creates an object that represents style modifications via stylesheet file(s) or/and CSS rules. Stylesheet file URL(s) are verified to be local to an add-on, while CSS rules are virified to be a string or array of strings. The style created can be applied to a content by calling `attach`, and removed using `detach`. Those functions are part of [content/mod](modules/sdk/content/mod.html) module. @param options {object} Options for the style. All these options are optional. Although if you don't supply any stylesheet or CSS rules, your style won't be very useful. @prop uri {string,array} A string, or an array of strings, that represents local URI to stylesheet. @prop source {string,array} A string, or an array of strings, that contains CSS rules. Those rules are applied after the rules in the stylesheet specified with `uri` options, if provided. @prop [type="author"] {string} The type of the sheet. It accepts the following values: `"agent"`, `"user"` and `"author"`. If not provided, the default value is `"author"`. @property {string} An array of strings that contains the CSS rule(s) specified in the constructor's option; `null` if no `source` option was given to the constructor. This property is read-only. @property {string} An array of strings that contains the stylesheet local URI(s) specified in the constructor's option; `null` if no `uri` option was given to the constructor. This property is read-only. @property {string} The type of the sheet. If no type is provided in constructor's option, it returns the default value, `"author"`. This property is read-only.