Apply “58 bytes of CSS to look great nearly everywhere”[1]

[1]: https://gist.github.com/JoeyBurzynski/617fb6201335779f8424ad9528b72c41

src/less/include/common.less

@@ -1,5 +1,13 @@
 @import 'colors';
 
+html {
+  max-width: 70ch;
+  padding: 3em 1em;
+  margin: auto;
+  line-height: 1.75;
+  font-size: 1.25em;
+}
+
 a {
   text-decoration: underline;
 
@@ -31,10 +39,6 @@ a {
 body {
   border: 0;
   font-family: "PT Sans", "Liberation Sans", "DejaVu Sans", "Tahoma", "Verdana", "Arial", sans-serif;
-  font-size: 15pt;
-  margin: 0;
-  padding: 0;
-  line-height: 160%;
 
   @media (prefers-color-scheme: dark) {
     background-color: @dark-background;
@@ -47,6 +51,10 @@ body {
   }
 }
 
+h1, h2, h3, h4, h5, h6 {
+  margin: 3em 0 1em;
+}
+
 h1 {
   font-size: 1.6rem;
 }
@@ -81,3 +89,7 @@ pre {
 }
 
 p { margin: 0; }
+
+p, ul, ol, dl {
+  margin-bottom: 2em;
+}