Adding analyzer project

Contains two analyzers with fixes

* Use AnsiConsole over System.Console
* Favor local instance over static implementation

src/Spectre.Console.Analyzer/Descriptors.cs

@@ -0,0 +1,49 @@
+using System.Collections.Concurrent;
+using Microsoft.CodeAnalysis;
+using static Microsoft.CodeAnalysis.DiagnosticSeverity;
+using static Spectre.Console.Analyzer.Descriptors.Category;
+
+namespace Spectre.Console.Analyzer
+{
+    /// <summary>
+    /// Code analysis descriptors.
+    /// </summary>
+    public static class Descriptors
+    {
+        internal enum Category
+        {
+            Usage, // 1xxx
+        }
+
+        private static readonly ConcurrentDictionary<Category, string> _categoryMapping = new();
+
+        private static DiagnosticDescriptor Rule(string id, string title, Category category, DiagnosticSeverity defaultSeverity, string messageFormat, string? description = null)
+        {
+            var helpLink = $"https://spectreconsole.net/spectre.console.analyzers/rules/{id}";
+            const bool IsEnabledByDefault = true;
+            return new DiagnosticDescriptor(id, title, messageFormat, _categoryMapping.GetOrAdd(category, c => c.ToString()), defaultSeverity, IsEnabledByDefault, description, helpLink);
+        }
+
+        /// <summary>
+        /// Gets definitions of diagnostics Spectre1000.
+        /// </summary>
+        public static DiagnosticDescriptor S1000_UseAnsiConsoleOverSystemConsole { get; } =
+            Rule(
+                "Spectre1000",
+                "Use AnsiConsole instead of System.Console",
+                Usage,
+                Warning,
+                "Use AnsiConsole instead of System.Console");
+
+        /// <summary>
+        /// Gets definitions of diagnostics Spectre1010.
+        /// </summary>
+        public static DiagnosticDescriptor S1010_FavorInstanceAnsiConsoleOverStatic { get; } =
+            Rule(
+                "Spectre1010",
+                "Favor the use of the instance of AnsiConsole over the static helper.",
+                Usage,
+                Info,
+                "Favor the use of the instance of AnsiConsole over the static helper.");
+    }
+}