feat: Change default font sizes - MEED-7147 - Meeds-io/MIPs#144 (#624)

This change will apply new font sizes:
- Title: 20px, regularColor, Bold
- Header: 18px, lowImportanceColor, Regular
- Body: 16px, regularColor, Regular
- Subtitle: 12px, lowImportanceColor, Regular

commons-extension-webapp/src/main/webapp/ckeditor/skins/common/variables.less

@@ -30,7 +30,7 @@
 @titleLineHeight: 1.2;
 @titleMarginBottom: 10px;
 @normalFontWeight: @textFontWeight;
-@codeFontSize: 14px;
+@codeFontSize: 16px;
 @listMargin: 0 0 10px 25px;
 @listPadding: 0 25px;
 @linkColor: #0782C1;