Support Org center block

Fixes https://github.com/kaushalmodi/ox-hugo/issues/148.

ox-blackfriday.el

@@ -79,7 +79,8 @@ Note that this variable is *only* for internal use.")
   ;;           (lambda (a s v b)
   ;;             (if a (org-blackfriday-export-to-markdown t s v)
   ;;               (org-open-file (org-blackfriday-export-to-markdown nil s v)))))))
-  :translate-alist '((example-block . org-blackfriday-example-block)
+  :translate-alist '((center-block . org-blackfriday-center-block)
+                     (example-block . org-blackfriday-example-block)
                      (fixed-width . org-blackfriday-fixed-width) ;Org Babel Results
                      (footnote-reference . org-blackfriday-footnote-reference)
                      (inner-template . org-blackfriday-inner-template)
@@ -387,6 +388,14 @@ style tag."
 
 ;;; Transcode Functions
 
+;;;; Center Block
+(defun org-blackfriday-center-block (_center-block contents _info)
+  "Center-align the text in CONTENTS using CSS."
+  (let* ((class "org-center")
+         (style (format ".%s { margin-left: auto; margin-right: auto; text-align: center; }" class)))
+    (format "<style>%s</style>\n\n<div class=\"%s\">\n  <div></div>\n\n%s\n</div>" ;See footnote 1
+            style class contents)))
+
 ;;;; Example Block
 (defun org-blackfriday-example-block (example-block _contents info)
   "Transcode an EXAMPLE-BLOCK element into Blackfriday Markdown format.

test/site/content-org/all-posts.org

@@ -1937,7 +1937,8 @@ Hash char at beginning of a continued line
 Markdown]
 
 This ! does not need to be escaped as there is no ambiguity.
-** Force line break                                        :force:line_break:
+** Force line break / Center align                         :force:line_break:
+*** Force line break
 :PROPERTIES:
 :EXPORT_FILE_NAME: force-line-break
 :END:
@@ -1950,6 +1951,33 @@ enforce a line break within a paragraph, use ‘\\’ at the end of a line.
 
 Line 1 \\
 Line 2
+*** Center align                                               :center_align:
+:PROPERTIES:
+:EXPORT_FILE_NAME: center-align
+:END:
+From [[https://orgmode.org/manual/Paragraphs.html][=C-h i g (org) Paragraphs=]]:
+
+#+begin_quote
+If you would like to center some text, do it like this:
+
+#+begin_src org
+,#+begin_center
+Everything should be made as simple as possible, \\
+but not any simpler
+,#+end_center
+#+end_src
+#+end_quote
+
+#+begin_center
+Everything should be made as simple as possible, \\
+but not any simpler
+#+end_center
+**** Testing emphasis in Org center block
+#+begin_center
+*bold* \\
+/italics/ \\
++strikethrough+
+#+end_center
 * Page Bundles                                                 :page_bundles:
 :PROPERTIES:
 :EXPORT_HUGO_SECTION: bundles

test/site/content/posts/center-align.md

@@ -0,0 +1,40 @@
++++
+title = "Center align"
+tags = ["body", "force", "line-break", "center-align"]
+draft = false
++++
+
+From [`C-h i g (org) Paragraphs`](https://orgmode.org/manual/Paragraphs.html):
+
+> If you would like to center some text, do it like this:
+>
+> ```org
+> #+begin_center
+> Everything should be made as simple as possible, \\
+> but not any simpler
+> #+end_center
+> ```
+
+<style>.org-center { margin-left: auto; margin-right: auto; text-align: center; }</style>
+
+<div class="org-center">
+  <div></div>
+
+Everything should be made as simple as possible, <br />
+but not any simpler
+
+</div>
+
+
+## Testing emphasis in Org center block {#testing-emphasis-in-org-center-block}
+
+<style>.org-center { margin-left: auto; margin-right: auto; text-align: center; }</style>
+
+<div class="org-center">
+  <div></div>
+
+**bold** <br />
+_italics_ <br />
+~~strikethrough~~
+
+</div>