Copy the image and paste it directly into markdown file.
GitHub will create an img tag for you. For example, after pasting an
image copied from the desktop, GitHub generated the img tag as follows:
<img width="436" alt="anchors" src="https://user-images.githubusercontent
.com/92759824/155658569-ecf8461a-c96f-4b76-8b55-d774ab4418ad.png">
The alt tag was populated with the image name.