fix: correct encoding of spaces in share URLs (#835)

Resolves #835

_includes/post-sharing.html

@@ -6,6 +6,7 @@
   <span class="share-label text-muted mr-1">{{ site.data.locales[site.lang].post.share }}</span>
   <span class="share-icons">
     {% capture title %}{{ page.title }} - {{ site.title }}{% endcapture %}
+    {% assign title = title | uri_escape %}
     {% assign url = page.url | absolute_url | url_encode %}
 
     {% for share in site.data.share.platforms %}