Merge pull request #304 from LCSB-BioCore/mo-update-contribution

 Add emoji references

.github/CONTRIBUTING.md

@@ -167,9 +167,10 @@ submitting the pull requests.
 1. **Make a fork of the repository**, commit the modifications in a **separate
    branch** and push the branch to your fork.
 2. Make a pull request where you describe the motivation and expected outcome
-   for the users. Specifically, consider any possible incompatibilities, and
-   the necessity to increment the version number after your changes are
-   applied.
+   for the users. Specifically, consider any possible incompatibilities, and the
+   necessity to increment the version number after your changes are applied.
+   Label your pull request with a [semantic emoji](https://gitmoji.dev/) in the
+   title to indicate what it addresses.
 3. After submitting the pull request, verify that all status checks (tests,
    documentation) are passing. Make sure any new contribution is properly
    documented and tested (you may want to check with coverage tools, using