Adding new project 'TUI'

I couldn't decide if CLI would implement a more traditional, unix-ish
commandline tool style or if I wanted a more stylish, TUI design, so I
separated those into two different projects.

TUI/TUI.csproj

@@ -0,0 +1,10 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net7.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>