Add Visual Studio extension for Linux platform support

VSIX extension that adds:
- "OpenMaui Linux App" project template in File → New → Project
- Pre-configured launch profiles for Linux debugging
- WSL integration for Windows developers
- x64 and ARM64 build configurations

Launch Profiles included:
- Linux (Local) - Direct execution
- Linux (WSL) - Run via WSL
- Linux (x64 Release) - Release build for x64
- Linux (ARM64 Release) - Release build for ARM64
- Publish Linux x64/ARM64 - Self-contained publishing

Build with: msbuild /p:Configuration=Release
Output: OpenMaui.VisualStudio.vsix

vsix/OpenMaui.VisualStudio/ProjectTemplates/OpenMauiLinuxApp/OpenMauiLinuxApp.csproj

@@ -0,0 +1,39 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net9.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <RootNamespace>$safeprojectname$</RootNamespace>
+    <AssemblyName>$safeprojectname$</AssemblyName>
+    <ApplicationTitle>$projectname$</ApplicationTitle>
+
+    <!-- Linux Runtime -->
+    <RuntimeIdentifiers>linux-x64;linux-arm64</RuntimeIdentifiers>
+  </PropertyGroup>
+
+  <PropertyGroup Condition="'$(Configuration)' == 'Debug'">
+    <DefineConstants>$(DefineConstants);DEBUG</DefineConstants>
+  </PropertyGroup>
+
+  <PropertyGroup Condition="'$(Configuration)' == 'Release'">
+    <PublishSingleFile>true</PublishSingleFile>
+    <SelfContained>true</SelfContained>
+    <PublishTrimmed>false</PublishTrimmed>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <!-- OpenMaui Linux Platform -->
+    <PackageReference Include="OpenMaui.Controls.Linux" Version="1.0.0-preview.*" />
+
+    <!-- Core MAUI packages -->
+    <PackageReference Include="Microsoft.Maui.Controls" Version="9.0.*" />
+    <PackageReference Include="Microsoft.Maui.Graphics" Version="9.0.*" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <EmbeddedResource Include="Resources\**\*" />
+  </ItemGroup>
+
+</Project>