docs: fix markdown (aquasecurity#553)

Correct markdown for MicroScanner link

README.md

@@ -315,7 +315,7 @@ $ docker run --rm -it alpine:3.11
 ```
 
 ## Embed in Dockerfile
-Scan your image as part of the build process by embedding Trivy in the Dockerfile. This approach can be used to update Dockerfiles currently using Aqua’s [Microscanner][https://github.com/aquasecurity/microscanner].
+Scan your image as part of the build process by embedding Trivy in the Dockerfile. This approach can be used to update Dockerfiles currently using Aqua’s [Microscanner](https://github.com/aquasecurity/microscanner).
 
 ```
 $ cat Dockerfile