feat: make post description customizable (#1602)

---------

Co-authored-by: Cotes Chung <11371340+cotes2020@users.noreply.github.com>

_posts/2019-08-08-text-and-typography.md

@@ -1,5 +1,6 @@
 ---
 title: Text and Typography
+description: Examples of text, typography, math equations, diagrams, flowcharts, pictures, videos, and more.
 author: cotes
 date: 2019-08-08 11:33:00 +0800
 categories: [Blogging, Demo]
@@ -13,8 +14,6 @@ image:
   alt: Responsive rendering of Chirpy theme on multiple devices.
 ---
 
-This post is to show Markdown syntax rendering on [**Chirpy**](https://github.com/cotes2020/jekyll-theme-chirpy/fork), you can also use it as an example of writing. Now, let's start looking at text and typography.
-
 ## Headings
 
 <!-- markdownlint-capture -->

_posts/2019-08-08-write-a-new-post.md

@@ -73,6 +73,18 @@ Having said that, the key `author` can also identify multiple entries.
 > The benefit of reading the author information from the file `_data/authors.yml`{: .filepath } is that the page will have the meta tag `twitter:creator`, which enriches the [Twitter Cards](https://developer.twitter.com/en/docs/twitter-for-websites/cards/guides/getting-started#card-and-content-attribution) and is good for SEO.
 {: .prompt-info }
 
+### Post Description
+
+By default, the first words of the post are used to display on the home page for a list of posts, in the _Further Reading_ section, and in the XML of the RSS feed. If you don't want to display the auto-generated description for the post, you can customize it using the `description` field in the _Front Matter_ as follows:
+
+```yaml
+---
+description: Short summary of the post.
+---
+```
+
+Additionally, the `description` text will also be displayed under the post title on the post's page.
+
 ## Table of Contents
 
 By default, the **T**able **o**f **C**ontents (TOC) is displayed on the right panel of the post. If you want to turn it off globally, go to `_config.yml`{: .filepath} and set the value of variable `toc` to `false`. If you want to turn off TOC for a specific post, add the following to the post's [Front Matter](https://jekyllrb.com/docs/front-matter/):

_posts/2019-08-09-getting-started.md

@@ -1,5 +1,8 @@
 ---
 title: Getting Started
+description: >-
+  Get started with Chirpy basics in this comprehensive overview.
+  You will learn how to install, configure, and use your first Chirpy-based website, as well as deploy it to a web server.
 author: cotes
 date: 2019-08-09 20:55:00 +0800
 categories: [Blogging, Tutorial]