docs: update estimated reading time blog post (satnaing#354)

Resolves satnaing#350

Author: satnaing

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

@@ -33,7 +33,9 @@ export function remarkReadingTime() {
   return function (tree, { data }) {
     const textOnPage = toString(tree);
     const readingTime = getReadingTime(textOnPage);
-    data.astro.frontmatter.readingTime = readingTime.text;
+    // readingTime.text will give us minutes read as a friendly string,
+    // i.e. "3 min read"
+    data.astro.frontmatter.minutesRead = readingTime.text;
   };
 }
 ```
@@ -88,15 +90,19 @@ export const collections = { blog };
 Step (5) Create a new file called `getPostsWithRT.ts` under `src/utils` directory.
 
 ```ts
-import type { MarkdownInstance } from "astro";
 import type { CollectionEntry } from "astro:content";
 import { slugifyStr } from "./slugify";
 
+interface Frontmatter {
+  frontmatter: {
+    title: string;
+    minutesRead: string;
+  };
+}
+
 export const getReadingTime = async () => {
   // Get all posts using glob. This is to get the updated frontmatter
-  const globPosts = import.meta.glob("../content/blog/*.md") as Promise<
-    CollectionEntry<"blog">["data"][]
-  >;
+  const globPosts = import.meta.glob<Frontmatter>("../content/blog/*.md");
 
   // Then, set those frontmatter value in a JS Map with key value pair
   const mapFrontmatter = new Map();
@@ -106,7 +112,7 @@ export const getReadingTime = async () => {
       const { frontmatter } = await globPost();
       mapFrontmatter.set(
         slugifyStr(frontmatter.title),
-        frontmatter.readingTime
+        frontmatter.minutesRead
       );
     })
   );
@@ -125,7 +131,7 @@ const getPostsWithRT = async (posts: CollectionEntry<"blog">[]) => {
 export default getPostsWithRT;
 ```
 
-Step (6) Refactor `getStaticPaths` of `/src/pages/posts/[slug].astro` as the following
+Step (6) Refactor `getStaticPaths` of `/src/pages/posts/[slug]/index.astro` as the following
 
 ```ts
 ---
@@ -212,7 +218,7 @@ Files that use `getSortedPosts` function are as follow
 - src/pages/posts/index.astro
 - src/pages/rss.xml.ts
 - src/pages/posts/index.astro
-- src/pages/posts/[slug].astro
+- src/pages/posts/[slug]/index.astro
 - src/utils/getPostsByTag.ts
 
 All you have to do is like this