Add theme support

[Blake-goofy]

Currently I only added support for settings, about, and data transfer windows. Planning on doing more soon.

Before

After

[Blake-goofy]

I just removed AllUsers="true" to make install easier for testing.

[alex-bochkov]

Could you please try to reduce the code duplication where possible? I think a ResourceDictionary might help here.
The same applies to the C# code. I want to make sure it is easy to reuse and not too difficult to hook into a new form.

**ChatGPT**
1) ResourceDictionary (most common for shared UI pieces, styles, templates)
Define reusable pieces in a separate .xaml file: SharedResources.xaml

<ResourceDictionary
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">

    <Style x:Key="MyButtonStyle" TargetType="Button">
        <Setter Property="Background" Value="LightBlue"/>
    </Style>

</ResourceDictionary>

Reference it in another XAML:

<Window.Resources>
    <ResourceDictionary>
        <ResourceDictionary.MergedDictionaries>
            <ResourceDictionary Source="SharedResources.xaml"/>
        </ResourceDictionary.MergedDictionaries>
    </ResourceDictionary>
</Window.Resources>

[Blake-goofy]

Yes, I will keep that in mind moving forward. Thanks for the feedback.

[Blake-goofy]

@alex-bochkov, I took the liberty of attempting to harmonize the tools window headings to match the GitHub sync window. I like the link to the wiki (see image in the top comment).