feat: support to pin articles (#50)

This feature can allow you to top articles via post front meta
property `top`, the value is a number, the smaller the number is,
the higher priority the article has.

Example:

```
title: My Article
top: <number>
```

5 files changed, 61 insertions, 32 deletions

diff --git a/_includes/views/pagination-item.html b/_includes/views/pagination-item.html
new file mode 100644
index 0000000..bea6d91
--- /dev/null
+++ b/_includes/views/pagination-item.html
@@ -0,0 +1,32 @@
+{%- assign date_format = site.yat.date_format | default: "%b %-d, %Y" -%}
+
+{% assign article = post.content %}
+{% assign lang = post.lang %}
+{%- include functions.html func='get_reading_time' -%}
+{% assign reading_time = return %}
+{%- include functions.html func='get_article_excerpt' -%}
+{% assign excerpt = return %}
+{%- assign post_url = post.url | relative_url -%}
+
+<li class="{{ post_item_class }}">
+  <h2 class="post-title">
+    <a class="post-link" href="{{ post_url }}">
+      {{ post.title | escape }}
+      {%- include views/post-badges.html -%}
+    </a>
+  </h2>
+  <div class="post-meta">
+    <span class="post-date"><i class="fa fa-calendar"></i> {{ post.date | date: date_format }}</span>
+    <span class="post-reading-time left-vsplit"><i class="fa fa-clock-o"></i> {{ reading_time }}</span>
+  </div>
+  <a class="post-excerpt" href="{{ post_url }}">
+    <p>
+    {{ excerpt }} <span class="read_more">Read More</span>
+    </p>
+  </a>
+  <div class="post-tags">
+    {%- for tag in post.tags -%}
+    <a class="post-tag" href="{{ '/tags.html ' | relative_url }}#{{tag}}">#{{tag}}</a>
+    {%- endfor -%}
+  </div>
+</li>
diff --git a/_includes/views/pagination.html b/_includes/views/pagination.html
index 88be011..014df85 100644
--- a/_includes/views/pagination.html
+++ b/_includes/views/pagination.html
@@ -8,38 +8,24 @@
 <div class="pagination">
   <!-- Post list links -->
   <ul class="post-list">
-    {%- for post in paginator.posts -%}
-    <li>
-      {%- assign date_format = site.yat.date_format | default: "%b %-d, %Y" -%}
-
-      {% assign article = post.content %}
-      {% assign lang = post.lang %}
-      {%- include functions.html func='get_reading_time' -%}
-      {% assign reading_time = return %}
-      {%- include functions.html func='get_article_excerpt' -%}
-      {% assign excerpt = return %}
-      {%- assign post_url = post.url | relative_url -%}
+    <!-- Top list item -->
+    {%- if paginator == site or paginator.page == 1 -%}
+      {%- assign post_item_class = "top-post" -%}
+      {%- assign posts = site.posts
+        | where_exp: "item", "item.top > 0"
+        | sort: "top" -%}
+      {%- for post in posts -%}
+        {%- include views/pagination-item.html -%}
+      {%- endfor -%}
+    {%- endif -%}
 
-      <h2 class="post-title">
-        <a class="post-link" href="{{ post_url }}">
-          {{ post.title | escape }}
-        </a>
-      </h2>
-      <div class="post-meta">
-        <span class="post-date"><i class="fa fa-calendar"></i> {{ post.date | date: date_format }}</span>
-        <span class="post-reading-time left-vsplit"><i class="fa fa-clock-o"></i> {{ reading_time }}</span>
-      </div>
-      <a class="post-excerpt" href="{{ post_url }}">
-        <p>
-        {{ excerpt }} <span class="read_more">Read More</span>
-        </p>
-      </a>
-      <div class="post-tags">
-        {%- for tag in post.tags -%}
-        <a class="post-tag" href="{{ '/tags.html ' | relative_url }}#{{tag}}">#{{tag}}</a>
-        {%- endfor -%}
-      </div>
-    </li>
+    <!-- Normal list item -->
+    {%- assign post_item_class = "" -%}
+    {%- for post in paginator.posts -%}
+      {%- if post.top -%}
+        {%- continue -%}
+      {%- endif -%}
+      {%- include views/pagination-item.html -%}
     {%- endfor -%}
   </ul>
 
diff --git a/_includes/views/post-badges.html b/_includes/views/post-badges.html
new file mode 100644
index 0000000..932781a
--- /dev/null
+++ b/_includes/views/post-badges.html
@@ -0,0 +1,4 @@
+<span class="post-badges">
+  <span class="post-badge badge-top">TOP</span>
+  <span class="post-badge badge-new">NEW</span>
+</span>
diff --git a/_includes/views/post-item.html b/_includes/views/post-item.html
index 0d6d129..0cad1f4 100644
--- a/_includes/views/post-item.html
+++ b/_includes/views/post-item.html
@@ -9,5 +9,6 @@
 <span>
   <a class="post-link" href="{{ post.url | relative_url }}">
     {{ post.title | escape }}
+    {%- include views/post-badges.html -%}
   </a>
 </span>
diff --git a/_includes/views/segments.html b/_includes/views/segments.html
index 2c92dc1..0cf9414 100644
--- a/_includes/views/segments.html
+++ b/_includes/views/segments.html
@@ -13,7 +13,13 @@
       {% assign items = site.posts | where: field, key %}
       {% for item in items %}
         {% if item != nil %}
-        <li> {% include views/post-item.html %} </li>
+          {%- assign post_item_class = "" -%}
+          {%- if item.top -%}
+            {%- assign post_item_class = "top-post" -%}
+          {%- endif -%}
+          <li class="{{ post_item_class }}">
+            {%- include views/post-item.html -%}
+          </li>
         {% endif %}
       {% endfor %}
     {% endfor %}