refactor: replace postSlug with Astro content slug

* refactor: replace postSlug with Astro content slug

Remove postSlug from blog schema. Refactor articles that use postSlug. Remove slugify function from slugify util file. Replace slugify logic with Astro's content collections slug logic.

Closes: #186

* docs: update docs for removed slugify contents

* refactor: remove unused import

src/content/blog/how-to-add-an-estimated-reading-time.md

@@ -2,8 +2,8 @@
 title: How to add an estimated reading time in AstroPaper
 author: Sat Naing
 pubDatetime: 2023-07-21T10:11:06.130Z
-modDatetime: 2023-12-21T05:03:41.955Z
-postSlug: how-to-add-estimated-reading-time
+modDatetime: 2023-12-26T08:39:25.181Z
+slug: how-to-add-estimated-reading-time
 featured: false
 draft: false
 tags:
@@ -89,8 +89,8 @@ Step (5) Create a new file called `getPostsWithRT.ts` under `src/utils` director
 
 ```ts
 import type { MarkdownInstance } from "astro";
-import slugify from "./slugify";
 import type { CollectionEntry } from "astro:content";
+import { slugifyStr } from "./slugify";
 
 export const getReadingTime = async () => {
   // Get all posts using glob. This is to get the updated frontmatter
@@ -104,7 +104,10 @@ export const getReadingTime = async () => {
   await Promise.all(
     globPostsValues.map(async globPost => {
       const { frontmatter } = await globPost();
-      mapFrontmatter.set(slugify(frontmatter), frontmatter.readingTime);
+      mapFrontmatter.set(
+        slugifyStr(frontmatter.title),
+        frontmatter.readingTime
+      );
     })
   );
 
@@ -114,7 +117,7 @@ export const getReadingTime = async () => {
 const getPostsWithRT = async (posts: CollectionEntry<"blog">[]) => {
   const mapFrontmatter = await getReadingTime();
   return posts.map(post => {
-    post.data.readingTime = mapFrontmatter.get(slugify(post.data));
+    post.data.readingTime = mapFrontmatter.get(slugifyStr(post.data.title));
     return post;
   });
 };
@@ -138,8 +141,8 @@ export async function getStaticPaths() {
 
   const postsWithRT = await getPostsWithRT(posts); // replace reading time logic with this func
 
-  const postResult = postsWithRT.map(post => ({ // make sure to replace posts with postsWithRT
-    params: { slug: slugify(post.data) },
+   const postResult = postsWithRT.map(post => ({ // make sure to replace posts with postsWithRT
+    params: { slug: post.slug },
     props: { post },
   }));