docs($location): update $location.search() jsdoc signature

Closes angular#8050

Author: jpsimons

src/ng/location.js

@@ -427,14 +427,17 @@ LocationHashbangInHtml5Url.prototype =
    * If the argument is a hash object containing an array of values, these values will be encoded
    * as duplicate search parameters in the url.
    *
-   * @param {(string|Array<string>)=} paramValue If `search` is a string, then `paramValue` will
-   * override only a single search property.
+   * @param {(string|Array<string>|boolean)=} paramValue If `search` is a string, then `paramValue`
+   * will override only a single search property.
    *
    * If `paramValue` is an array, it will override the property of the `search` component of
    * `$location` specified via the first argument.
    *
    * If `paramValue` is `null`, the property specified via the first argument will be deleted.
    *
+   * If `paramValue` is `true`, the property specified via the first argument will be added with no
+   * value nor trailing equal sign.
+   *
    * @return {Object} If called with no arguments returns the parsed `search` object. If called with
    * one or more arguments returns `$location` object itself.
    */