Add readme file

CleanCode.NET/CleanCode.NET.sln

@@ -35,6 +35,7 @@ EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution Items", "{EEEF2C42-209D-47E4-8D50-1BE65FB5E6C8}"
 	ProjectSection(SolutionItems) = preProject
 		CleanCodeNet.nuspec = CleanCodeNet.nuspec
+		Readme.md = Readme.md
 	EndProjectSection
 EndProject
 Global

CleanCode.NET/Readme.md

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+# Clean Code .NET
+Clean Code .NET is a set of Roslyn analyzers aimed to help developers build more correct and readable code.
+At this moment it contains 3 analyzers (hope to improve their count in future):
+
+## Switch analyzer
+Ensures that all possible cases are covered in ```switch``` statement for enums and pattern matching.
+Consider example:
+
+```csharp
+enum TestEnum
+{
+    Case1,
+    Case2,
+    Case3
+}
+
+switch (TestEnum.Case1)
+{
+    case Test.TestEnum.Case1: { break; }
+    case Test.TestEnum.Case2: { break; }
+    default: throw new NotImplementedException();
+}
+```
+Will give a warning, because:
+1. Intentionally specified that default case is not a normal case (throws exception).
+2. Not all possible cases are covered (TestEnum.Case3).
+It will allow developer to not miss handling of newly added enum values.
+
+## Constructor null analyzer
+Checks if constructor requires all reference type parameters to be not null and provide fixers for it:
+
+```csharp
+public Program(string test1, object test2, TestStruct<string> test3, string test4)
+{
+}
+```
+This example will be transformed into:
+```csharp
+public Program(string test1, object test2, TestStruct<string> test3, string test4)
+{
+    if (test1 == null)
+        throw new ArgumentNullException(nameof(test1));
+    if (test2 == null)
+        throw new ArgumentNullException(nameof(test2));
+    if (test4 == null)
+        throw new ArgumentNullException(nameof(test4));
+}
+```
+Various options are provided: if-check, if + assignment coalesce (``` ?? throw new ArgumentNullException(nameof(param)) ```) where possible and ```Contract.Requires```
+
+## Named parameters analyzer
+Ensures if method/constructor calls has 4 or more parameters to have parameter names.
+For example:
+```csharp
+Method("Foo", "Bar", "Baz", "Qux");
+```
+Should be:
+```csharp
+Method(foo: "Foo", bar: "Bar", baz: "Baz", qux: "Qux");
+```
+
+## How to use
+There are 2 options:
+- Install nuget package to project(s) https://www.nuget.org/packages/CleanCodeNet. This is metapackage, you can install any of analyzers separately
+- Install Visual Studio extension https://marketplace.visualstudio.com/items?itemName=denis-prodan.clean-code-net