Switch from sln to slnx (#113)

Author: AArnott

DotNetRepoTools.sln

@@ -0,0 +1,29 @@
+<Solution>
+  <Folder Name="/Solution Items/">
+    <File Path=".editorconfig" />
+    <File Path="Directory.Build.props" />
+    <File Path="Directory.Build.targets" />
+    <File Path="Directory.Packages.props" />
+    <File Path="global.json" />
+    <File Path="nuget.config" />
+    <File Path="README.md" />
+    <File Path="stylecop.json" />
+    <File Path="version.json" />
+  </Folder>
+  <Folder Name="/Solution Items/src/">
+    <File Path="src/.editorconfig" />
+    <File Path="src/Directory.Build.props" />
+    <File Path="src/Directory.Build.targets" />
+  </Folder>
+  <Folder Name="/Solution Items/test/">
+    <File Path="test/.editorconfig" />
+    <File Path="test/Directory.Build.props" />
+    <File Path="test/Directory.Build.targets" />
+  </Folder>
+  <Folder Name="/src/">
+    <Project Path="src/Nerdbank.DotNetRepoTools/Nerdbank.DotNetRepoTools.csproj" />
+  </Folder>
+  <Folder Name="/test/">
+    <Project Path="test/Nerdbank.DotNetRepoTools.Tests/Nerdbank.DotNetRepoTools.Tests.csproj" />
+  </Folder>
+</Solution>