Update footer.md

HarikumarG · mansona · commit 118595c78410 · 2020-06-25T14:24:21.000+01:00
diff --git a/docs/components/footer.md b/docs/components/footer.md
@@ -3,3 +3,9 @@
 ```handlebars
 <EsFooter />
 ```
+
+You can also add a "contribute to this page" link in the footer by passing `@contributeLink`:
+
+```handlebars
+<EsFooter @contributeLink="https://github.com/ember-learn/ember-website" />
+```
