Add support for reactions plugin (#180)

source/plugins/reactions/README.md

@@ -0,0 +1,24 @@
+### 🎭 Comment reactions
+
+The *reactions* plugin displays overall reactions on your recent issues and issue comments.
+
+<table>
+  <td align="center">
+    <img src="https://github.com/lowlighter/lowlighter/blob/master/metrics.plugin.reactions.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_reactions: yes
+    plugin_reactions_limit: 200          # Compute reactions over last 200 issue comments
+    plugin_reactions_days: 14            # Compute reactions on issue comments posted less than 14 days ago
+    plugin_reactions_details: percentage # Display reactions percentage
+```