fix a typo in image-keyboard-response description (#2876)

Author: dillonplunkett

docs/plugins/image-keyboard-response.md

@@ -2,7 +2,7 @@
 
 Current version: 1.1.2. [See version history](https://github.com/jspsych/jsPsych/blob/main/packages/plugin-image-keyboard-response/CHANGELOG.md).
 
-This plugin displays and image and records responses generated with the keyboard. The stimulus can be displayed until a response is given, or for a pre-determined amount of time. The trial can be ended automatically if the participant has failed to respond within a fixed length of time.
+This plugin displays an image and records responses generated with the keyboard. The stimulus can be displayed until a response is given, or for a pre-determined amount of time. The trial can be ended automatically if the participant has failed to respond within a fixed length of time.
 
 Image files can be automatically preloaded by jsPsych using the [`preload` plugin](preload.md). However, if you are using timeline variables or another dynamic method to specify the image stimulus, you will need to [manually preload](../overview/media-preloading.md#manual-preloading) the images.