Update GitHub light color palette (#998)

I noticed that the current syntax highlighting generator uses an older
color palette that doesn’t reflect GitHub’s latest light theme, which
now features lighter, pastel tones for improved readability and
accessibility. I’ve updated the color scheme to match the newer colors.

I was wondering if it makes sense to adopt these changes or, if
maintaining the current color scheme is essential, whether it would be
better to publish this as a separate variant under a different name.

## Example

### Before 

![before](https://github.com/user-attachments/assets/7cb6f80b-f7c5-4071-8531-5aa7c338bcf4)

### After

![after](https://github.com/user-attachments/assets/dfb7930d-4ef5-4797-bf6c-2a35ae23d43e)

styles/github.xml

@@ -1,44 +1,39 @@
 <style name="github">
-  <entry type="Error" style="#a61717 bg:#e3d2d2"/>
+  <entry type="Error" style="#f6f8fa bg:#82071e"/>
   <entry type="Background" style="bg:#ffffff"/>
-  <entry type="Keyword" style="bold #000000"/>
-  <entry type="KeywordType" style="bold #445588"/>
-  <entry type="NameAttribute" style="#008080"/>
-  <entry type="NameBuiltin" style="#0086b3"/>
-  <entry type="NameBuiltinPseudo" style="#999999"/>
-  <entry type="NameClass" style="bold #445588"/>
-  <entry type="NameConstant" style="#008080"/>
-  <entry type="NameDecorator" style="bold #3c5d5d"/>
-  <entry type="NameEntity" style="#800080"/>
-  <entry type="NameException" style="bold #990000"/>
-  <entry type="NameFunction" style="bold #990000"/>
+  <entry type="Keyword" style="#cf222e"/>
+  <entry type="KeywordType" style="#cf222e"/>
+  <entry type="NameAttribute" style="#1f2328"/>
+  <entry type="NameBuiltin" style="#6639ba"/>
+  <entry type="NameBuiltinPseudo" style="#6a737d"/>
+  <entry type="NameClass" style="#1f2328"/>
+  <entry type="NameConstant" style="#0550ae"/>
+  <entry type="NameDecorator" style="#0550ae"/>
+  <entry type="NameEntity" style="#6639ba"/>
+  <entry type="NameFunction" style="#6639ba"/>
   <entry type="NameLabel" style="bold #990000"/>
-  <entry type="NameNamespace" style="#555555"/>
-  <entry type="NameTag" style="#000080"/>
-  <entry type="NameVariable" style="#008080"/>
-  <entry type="NameVariableClass" style="#008080"/>
-  <entry type="NameVariableGlobal" style="#008080"/>
-  <entry type="NameVariableInstance" style="#008080"/>
-  <entry type="LiteralString" style="#dd1144"/>
-  <entry type="LiteralStringRegex" style="#009926"/>
-  <entry type="LiteralStringSymbol" style="#990073"/>
-  <entry type="LiteralNumber" style="#009999"/>
-  <entry type="Operator" style="bold #000000"/>
-  <entry type="Comment" style="italic #999988"/>
-  <entry type="CommentMultiline" style="italic #999988"/>
-  <entry type="CommentSingle" style="italic #999988"/>
-  <entry type="CommentSpecial" style="bold italic #999999"/>
-  <entry type="CommentPreproc" style="bold #999999"/>
-  <entry type="GenericDeleted" style="#000000 bg:#ffdddd"/>
-  <entry type="GenericEmph" style="italic #000000"/>
-  <entry type="GenericError" style="#aa0000"/>
-  <entry type="GenericHeading" style="#999999"/>
-  <entry type="GenericInserted" style="#000000 bg:#ddffdd"/>
-  <entry type="GenericOutput" style="#888888"/>
-  <entry type="GenericPrompt" style="#555555"/>
-  <entry type="GenericStrong" style="bold"/>
-  <entry type="GenericSubheading" style="#aaaaaa"/>
-  <entry type="GenericTraceback" style="#aa0000"/>
+  <entry type="NameNamespace" style="#24292e"/>
+  <entry type="NameOther" style="#1f2328"/>
+  <entry type="NameTag" style="#0550ae"/>
+  <entry type="NameVariable" style="#953800"/>
+  <entry type="NameVariableClass" style="#953800"/>
+  <entry type="NameVariableGlobal" style="#953800"/>
+  <entry type="NameVariableInstance" style="#953800"/>
+  <entry type="LiteralString" style="#0a3069"/>
+  <entry type="LiteralStringRegex" style="#0a3069"/>
+  <entry type="LiteralStringSymbol" style="#032f62"/>
+  <entry type="LiteralNumber" style="#0550ae"/>
+  <entry type="Operator" style="#0550ae"/>
+  <entry type="Comment" style="#57606a"/>
+  <entry type="CommentMultiline" style="#57606a"/>
+  <entry type="CommentSingle" style="#57606a"/>
+  <entry type="CommentSpecial" style="#57606a"/>
+  <entry type="CommentPreproc" style="#57606a"/>
+  <entry type="GenericDeleted" style="#82071e bg:#ffebe9"/>
+  <entry type="GenericEmph" style="#1f2328"/>
+  <entry type="GenericInserted" style="#116329 bg:#dafbe1"/>
+  <entry type="GenericOutput" style="#1f2328"/>
   <entry type="GenericUnderline" style="underline"/>
-  <entry type="TextWhitespace" style="#bbbbbb"/>
+  <entry type="Punctuation" style="#1f2328"/>
+  <entry type="TextWhitespace" style="#ffffff"/>
 </style>