Modernize code, improve packaging

We can simply depend on JsonPoke as a dependency, which will automatically bring into MSBuild the JsonPoke task we use, no need to complicate packaging for that.

Clean root folder structure by moving img under assets, update some screenshots and readme wording.

Also add a package-level readme with better selective content inclusion.

Author: kzu

SmallSharp.sln

@@ -1,28 +1,20 @@
 
 Microsoft Visual Studio Solution File, Format Version 12.00
-# Visual Studio Version 16
-VisualStudioVersion = 16.0.30516.212
+# Visual Studio Version 17
+VisualStudioVersion = 17.5.33103.201
 MinimumVisualStudioVersion = 10.0.40219.1
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution Items", "{5420D663-3EA6-419B-8F73-C7EA374CFBBE}"
 	ProjectSection(SolutionItems) = preProject
 		.editorconfig = .editorconfig
 		.netconfig = .netconfig
-		.github\dependabot.yml = .github\dependabot.yml
-		src\Directory.Build.props = src\Directory.Build.props
-		src\Directory.Build.targets = src\Directory.Build.targets
 		src\Directory.props = src\Directory.props
 		readme.md = readme.md
 	EndProjectSection
 EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "workflows", "workflows", "{FFAB61A4-707D-4C79-A364-BF259FA865BB}"
 	ProjectSection(SolutionItems) = preProject
 		.github\workflows\build.yml = .github\workflows\build.yml
-		.github\workflows\changelog.yml = .github\workflows\changelog.yml
-		.github\workflows\pages.yml = .github\workflows\pages.yml
 		.github\workflows\publish.yml = .github\workflows\publish.yml
-		.github\workflows\release-notes.yml = .github\workflows\release-notes.yml
-		.github\workflows\sponsors.ps1 = .github\workflows\sponsors.ps1
-		.github\workflows\sponsors.yml = .github\workflows\sponsors.yml
 	EndProjectSection
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "SmallSharp", "src\SmallSharp\SmallSharp.csproj", "{97648980-AA30-4AC0-B8E9-FCF6359F56A0}"