Add BaseDark and BaseLight theme file
ADD
WalletWasabi.Fluent/Styles/Themes/BaseDark.xaml
+<Styles xmlns="https://github.com/avaloniaui"
+ xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+ xmlns:sys="clr-namespace:System;assembly=netstandard"
+ xmlns:local="clr-namespace:AvalonStudio.Controls.Standard.CodeEditor;assembly=AvalonStudio.Controls.Standard">
+ <Styles.Resources>
+
+ </Styles.Resources>
+</Styles>

ADD
WalletWasabi.Fluent/Styles/Themes/BaseLight.xaml
+<Styles xmlns="https://github.com/avaloniaui"
+ xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+ xmlns:sys="clr-namespace:System;assembly=netstandard"
+ xmlns:local="clr-namespace:AvalonStudio.Controls.Standard.CodeEditor;assembly=AvalonStudio.Controls.Standard">
+ <Styles.Resources>
+
+ </Styles.Resources>
+</Styles>

Add BaseDark and BaseLight theme file