update docker info
MODIFY
README.md
README.md
@@ -156,7 +156,8 @@ Hence gcc-9 and especially llvm-9 should be the compilers of choice.
If your distribution does not have them, you can use the Dockerfile:
```shell
-$ docker build -t aflplusplus
+$ cd AFLplusplus
+$ sudo docker build -t aflplusplus .
```

update docker info