website: blog: Set blog posts' lang attribute to English.

Fixes <https://issues.guix.gnu.org/63977>.
Suggested by Maxime Devos <maximedevos@telenet.be>.

* website/apps/blog/templates/post.scm (post-t): Mark the post text as
English.
* website/apps/blog/templates/components.scm (post-preview): Likewise.

website/apps/blog/templates/components.scm

@@ -1,4 +1,5 @@
 ;;; GNU Guix web site
+;;; Copyright © 2023 Florian Pelz <pelzflorian@pelzflorian.de>
 ;;; Initially written by sirgazil who waives all
 ;;; copyright interest on this file.
 
@@ -27,13 +28,15 @@
   `(a
     (@ (class "item-preview")
        (href ,(guix-url (url-path-join (post-url-path post) ""))))
-    (h3 ,(post-ref post 'title))
+    (h3
+     (@ (lang "en"))
+     ,(post-ref post 'title))
     (p
      (@ (class "item-date"))
      ,(date->string (post-date post) (C_ "SRFI-19 date->string format"
                                          "~B ~e, ~Y")))
     (p
-     (@ (class "item-summary"))
+     (@ (class "item-summary") (lang "en"))
      ,(string-summarize (sxml->string* (post-sxml post)) 30)
      ,(C_ "blog post summary ellipsis" "…"))))
 

website/apps/blog/templates/post.scm

@@ -1,4 +1,5 @@
 ;;; GNU Guix web site
+;;; Copyright © 2023 Florian Pelz <pelzflorian@pelzflorian.de>
 ;;; Initially written by sirgazil who waives all
 ;;; copyright interest on this file.
 
@@ -38,10 +39,10 @@
      #:content
      `(main
        (article
-	(@ (class "page centered-block limit-width"))
+        (@ (class "page centered-block limit-width") (lang "en"))
 	(h2 ,(post-ref post 'title))
 	(p
-	 (@ (class "post-metadata centered-text"))
+         (@ (class "post-metadata centered-text") (lang ,%current-ietf-tag))
 	 ,(post-ref post 'author) " — "
          ,(date->string (post-date post) (C_ "SRFI-19 date->string format"
                                              "~B ~e, ~Y")))
@@ -50,7 +51,7 @@
           (syntax-highlight (post-sxml post)))
 
 	(div
-	 (@ (class "tag-list"))
+         (@ (class "tag-list") (lang ,%current-ietf-tag))
          ,(G_ `(p "Related topics:"))
 
 	 ,@(map
@@ -63,7 +64,7 @@
 	    (sort tags tag-first?)))
 
         (div
-         (@ (class "license"))
+         (@ (class "license") (lang ,%current-ietf-tag))
          ,(G_ `(p "Unless otherwise stated, blog posts on this site are
 copyrighted by their respective authors and published under the terms of
 the " ,(G_