Doc: Simple CSS style: Convert font-sizes from px to pt

Unlike other rendering backends, QTextBrowser treats px unit in
stylesheets as physical pixels when printing, resulting in
too small to read font sizes.

Work around this by converting font-size px units to pt.

Change-Id: I70c71d8bda0996f793bf1c4558775384fe6ec297
Task-number: QTBUG-51083
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@theqtcompany.com>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@theqtcompany.com>
Reviewed-by: Robert Loehning <robert.loehning@theqtcompany.com>

doc/global/template/style/offline-simple.css

 body {
-  font-size: 14px;
+  font-size: 10.5pt;
 }
 
 pre {
   background-color: #f0f0f0;
   font-family: Courier, monospace;
-  font-size: 15px;
+  font-size: 11pt;
   font-weight: 600;
   vertical-align: top;
   margin: 15px 85px 15px 35px;
@@ -41,7 +41,7 @@ a[href|="http://"], a[href|="https://"] {
 h1.title {
   margin-top: 30px;
   margin-left: 6px;
-  font-size: 32px;
+  font-size: 24pt;
   padding: 6px;
 }
 
@@ -52,7 +52,7 @@ h2, p.h2 {
 }
 
 h3 {
-  font-size: 16px;
+  font-size: 12pt;
   margin: 30px 0px 30px 6px;
 }
 
@@ -82,7 +82,7 @@ h3.fn, span.fn {
   padding: 5px;
   text-decoration: none;
   font-weight: 400;
-  font-size: 16px;
+  font-size: 12pt;
   margin: 45px 0px 0px 6px;
 }
 
@@ -107,7 +107,7 @@ table tr.odd {
 table.qmlname td {
   padding: 0px;
   margin-left: 6px;
-  font-size: 16px;
+  font-size: 12pt;
 }
 
 table.qmlname p .name,
@@ -125,12 +125,12 @@ h3.fn .name, h3.fn .type {
 }
 
 tr > td > pre {
-  font-size: 14px;
+  font-size: 10.5pt;
 }
 
 code {
   font-family: Courier, monospace;
-  font-size: 16px;
+  font-size: 12pt;
   font-weight: 400;
 }
 
@@ -167,7 +167,7 @@ td#buildversion {
 .footer, .footer p {
   padding: 5px 0px 5px 0px;
   margin: 45px 15px 5px 15px;
-  font-size: 10px;
+  font-size: 7.5pt;
   background-color: #cccccc;
 }