feat(emacs): Customise default CSS for HTML exports

users/crumb/programs/emacs/modules/syd-org.el

@@ -255,6 +255,32 @@ See https://lists.gnu.org/archive/html/emacs-orgmode/2019-07/msg00081.html."
               (org-agenda-entry-types '(:deadline))
               (org-agenda-overriding-header "Upcoming deadlines"))))))))
 
+(defvar syd-org-default-css "
+<style>
+  html
+  { height: 100%;
+  }
+  
+  body
+  { height: 100%
+  ; padding: 0 10px
+  ; line-height: 1.6
+  ; font-size: 18px
+  ; margin: 40px auto
+  ; max-width: 650px
+  ; color: #444
+  }
+  
+  h1, h2, h3
+  { line-height: 1.2
+  }
+  
+  pre
+  { line-height: normal
+  }
+</style>"
+  "A default style for Org HTML exports.")
+
 (use-package org
   :defer-incrementally
   calendar find-func format-spec org-macs org-compat org-faces org-entities
@@ -305,6 +331,8 @@ See https://lists.gnu.org/archive/html/emacs-orgmode/2019-07/msg00081.html."
            (org-enforce-todo-dependencies t)
            (org-image-actual-width nil)
            (org-imenu-depth 6)
+           ;; Include some sane default CSS declarations when exporting to HTML.
+           (org-html-head syd-org-default-css)
            ;; Don't right-align tags.
            (org-tags-column 0)
            (org-priority-faces '((?A . error)