docs: Add :Z to 'docker run -v' so that it works with Podman on Fedora (

fixes github-linguist#7159)

README.md

@@ -188,7 +188,7 @@ If you have Docker installed you can build an image and run Linguist within a co
 
 ```console
 $ docker build -t linguist .
-$ docker run --rm -v $(pwd):$(pwd) -w $(pwd) -t linguist
+$ docker run --rm -v $(pwd):$(pwd):Z -w $(pwd) -t linguist
 66.84%  264519     Ruby
 24.68%  97685      C
 6.57%   25999      Go