Add contributors plugin (#126)

source/plugins/contributors/README.md

@@ -0,0 +1,25 @@
+### 🏅 Contributors
+
+The *contributors* plugin lets you display repositories contributors from a commit range, that can be specified through either sha, tags, branch, etc.
+
+It's especially useful to acknowledge contributors on release notes.
+
+<table>
+  <td align="center">
+    <img src="https://github.com/lowlighter/lowlighter/blob/master/metrics.plugin.contributors.svg">
+    <img width="900" height="1" alt="">
+  </td>
+</table>
+
+#### ℹ️ Examples workflows
+
+[➡️ Available options for this plugin](metadata.yml)
+
+```yaml
+- uses: lowlighter/metrics@latest
+  with:
+    # ... other options
+    plugin_contributors: yes
+    plugin_contributors_base: ""     # Base reference (commit, tag, branch, etc.)
+    plugin_contributors_head: master # Head reference (commit, tag, branch, etc.)
+```