feat: add modified datetime in blog posts

* feat: add modified datetime in blog posts

Add modDatetime in blogSchema. Update Datetime component to accept modDatetime. Update sorting logic. Rename datetime to pubDatetime in Datetime component.

Closes: #134

* feat: add published_time & modified_time meta tags

* docs: update related blog posts to be up-to-date

* fix: remove extra spaces in breadcrumbs

src/components/Breadcrumbs.astro

@@ -16,7 +16,7 @@ breadcrumbList[0] === "posts" &&
   <ul>
     <li>
       <a href="/">Home</a>
-      <span aria-hidden="true">&nbsp;&gt;&nbsp;</span>
+      <span aria-hidden="true">&gt;</span>
     </li>
     {
       breadcrumbList.map((breadcrumb, index) =>
@@ -33,7 +33,7 @@ breadcrumbList[0] === "posts" &&
         ) : (
           <li>
             <a href={`/${breadcrumb}`}>{breadcrumb}</a>
-            <span aria-hidden="true">&nbsp;&gt;&nbsp;</span>
+            <span aria-hidden="true">&gt;</span>
           </li>
         )
       )