Merge pull request #202 from unsplash/add-plus-query-param

Add `Plus` search param

Author: Magellol

src/methods/search/index.ts

@@ -2,7 +2,7 @@ import { compactDefined } from '../../helpers/fp';
 import * as Query from '../../helpers/query';
 import { createRequestHandler, makeEndpoint } from '../../helpers/request';
 import { castResponse } from '../../helpers/response';
-import { OrientationParam, PaginationParams } from '../../types/request';
+import { OrientationParam, PaginationParams, Plus } from '../../types/request';
 import { ColorId, ContentFilter, Language, SearchOrderBy } from './types/request';
 import * as SearchResponse from './types/response';
 
@@ -19,6 +19,7 @@ type SearchPhotosParams = SearchParams &
      */
     orderBy?: SearchOrderBy;
     color?: ColorId;
+    plus?: Plus;
     /**
      * API defaults to `en` (English) if no value is provided
      */

src/types/request.ts

@@ -9,6 +9,7 @@ export type Orientation = 'landscape' | 'portrait' | 'squarish';
 export type OrientationParam = {
   orientation?: Orientation;
 };
+export type Plus = 'mixed' | 'only' | 'none';
 
 export type PaginationParams = {
   /**