Add additional contribution note about ci builds

CONTRIBUTING.md

@@ -13,7 +13,7 @@ If you want to add an entry to the `README.md` please consider this:
 - is the entry valuable to people trying to get things done in Rust?
 - if you want to add something, please use the template `[ACCOUNT/REPO](https://github.com/ACCOUNT/REPO) [[CRATE](https://crates.io/crates/CRATE)] — DESCRIPTION`
     * if you've not published your crate to `crates.io` remove the `[[CRATE](...)]` part.
-    * if you want to add a build badge put the image after the description, separated by a space. Please make sure to add the branch information to the image:
+    * if you have a CI build, please add the build badge. Put the image after the description, separated by a space. Please make sure to add the branch information to the image:
        * example for Travis: ` [<img src="https://api.travis-ci.org/XXX/CRATE.svg?branch=master">](https://travis-ci.org/XXX/CRATE)`
        * for Github actions please see https://docs.github.com/en/actions/configuring-and-managing-workflows/configuring-a-workflow#example-using-the-branch-parameter
 - please pay attention to the alphabetical ordering.