Add minimal alt text to README

Author: jsoref

README.md

@@ -7,11 +7,11 @@ The action is available for all public repositories, as well as private reposito
 
 You can see the results on the job logs:
 
-<img width="854" alt="Screen Shot 2022-03-31 at 1 10 51 PM" src="https://user-images.githubusercontent.com/2161/161042286-b22d7dd3-13cb-458d-8744-ce70ed9bf562.png">
+<img width="854" alt="GitHub workflow run log showing Dependency Review job output" src="https://user-images.githubusercontent.com/2161/161042286-b22d7dd3-13cb-458d-8744-ce70ed9bf562.png">
 
 or on the job summary:
 
-<img src="https://user-images.githubusercontent.com/7847935/182871416-50332bbb-b279-4621-a136-ca72a4314301.png">
+<img alt="GitHub job summary showing Dependency Review output" src="https://user-images.githubusercontent.com/7847935/182871416-50332bbb-b279-4621-a136-ca72a4314301.png">
 
 ## Installation