add link to CircleCI beta

Author: bahmutov

CONTRIBUTING.md

@@ -2,11 +2,13 @@ How to [code a plugin](https://github.com/netlify/build/blob/master/docs/creatin
 
 ## Testing and releasing a new version
 
-Try using `beta` branch to release new pre-release versions of the plugin by following [the semantic release guide](https://github.com/semantic-release/semantic-release/blob/master/docs/recipes/pre-releases.md). You can fork and test out new versions published to NPM using the [netlify-plugin-cypress-example](https://github.com/cypress-io/netlify-plugin-cypress-example) repository. Hope the `master` branch merged into `beta` does not bring features and fixes *already released*. Thus I suggest using `beta` branch for new features.
-
 If helps to install [Netlify CLI](https://github.com/netlify/cli) to test the plugin locally
 
 ```shell
 npm install netlify-cli -g
 netlify build
 ```
+
+Try using `beta` branch to release new pre-release versions of the plugin by following [the semantic release guide](https://github.com/semantic-release/semantic-release/blob/master/docs/recipes/pre-releases.md). You can fork and test out new versions published to NPM using the [netlify-plugin-cypress-example](https://github.com/cypress-io/netlify-plugin-cypress-example) repository. Hope the `master` branch merged into `beta` does not bring features and fixes *already released*. Thus I suggest using `beta` branch for new features.
+
+**Do not open pull request on CircleCI** while adding new features to the `beta` branch. If there is a pull request, semantic-release refuses to publish new versions. Instead just watch the [builds on CircleCI](https://circleci.com/gh/cypress-io/netlify-plugin-cypress/tree/beta) directly and open the PR after the new version has been tested.