Add stackoverflow plugin (#159)

source/plugins/stackoverflow/README.md

@@ -0,0 +1,36 @@
+### 🗨️ Stackoverflow plugin
+
+The *stackoverflow* plugin lets you display your metrics, questions and answer from [stackoverflow](https://stackoverflow.com/).
+
+<table>
+  <td align="center">
+    <img src="https://github.com/lowlighter/lowlighter/blob/master/metrics.plugin.stackoverflow.svg">
+    <img width="900" height="1" alt="">
+  </td>
+</table>
+
+<details>
+<summary>💬 Get your user id</summary>
+
+Go to [stackoverflow.com](https://stackoverflow.com/) and click on your account profile.
+
+Your user id will be in both url and search bar.
+
+![User id](/.github/readme/imgs/plugin_stackoverflow_user_id.png)
+
+</details>
+
+#### ℹ️ Examples workflows
+
+[➡️ Available options for this plugin](metadata.yml)
+
+```yaml
+- uses: lowlighter/metrics@latest
+  with:
+    # ... other options
+    plugin_stackoverflow: yes
+    plugin_stackoverflow_user: 8332505                           # Stackoverflow user id (required)
+    plugin_stackoverflow_sections: answers-top, questions-recent # Display top answers and recent questions
+    plugin_stackoverflow_limit: 2                                # Display 2 entries per section
+    plugin_stackoverflow_lines: 4                                # Display 4 lines per entry
+```