Add progress task list support

docs/input/progress.md

@@ -0,0 +1,78 @@
+Title: Progress
+Order: 5
+---
+
+Spectre.Console can display information about long running tasks in the console. 
+
+<img src="assets/images/progress.png" style="max-width: 100%;margin-bottom:20px;">
+
+If the current terminal isn't considered "interactive", such as when running 
+in a continuous integration system, or the terminal can't display 
+ANSI control sequence, any progress will be displayed in a simpler way.
+
+<img src="assets/images/progress_fallback.png" style="max-width: 100%;">
+
+# Usage
+
+```csharp
+// Synchronous
+AnsiConsole.Progress()
+    .Start(ctx => 
+    {
+        // Define tasks
+        var task1 = ctx.AddTask("[green]Reticulating splines[/]");
+        var task2 = ctx.AddTask("[green]Folding space[/]");
+
+        while(!ctx.IsFinished) 
+        {
+            task1.Increment(1.5);
+            task2.Increment(0.5);
+        }
+    });
+```
+
+## Asynchronous progress
+
+If you prefer to use async/await, you can use `StartAsync` instead of `Start`.
+
+```csharp
+// Asynchronous
+await AnsiConsole.Progress()
+    .StartAsync(async ctx =>
+    {
+        // Define tasks
+        var task1 = ctx.AddTask("[green]Reticulating splines[/]");
+        var task2 = ctx.AddTask("[green]Folding space[/]");
+
+        while (!ctx.IsFinished)
+        {
+            // Simulate some work
+            await Task.Delay(250);
+
+            // Increment
+            task1.Increment(1.5);
+            task2.Increment(0.5);
+        }
+    });
+```
+
+# Configure
+
+```csharp
+// Asynchronous
+AnsiConsole.Progress()
+    .AutoRefresh(false) // Turn off auto refresh
+    .AutoClear(false)   // Do not remove the task list when done
+    .Columns(new ProgressColumn[] 
+    {
+        new TaskDescriptionColumn(),    // Task description
+        new ProgressBarColumn(),        // Progress bar
+        new PercentageColumn(),         // Percentage
+        new RemainingTimeColumn(),      // Remaining time
+        new SpinnerColumn(),            // Spinner
+    })
+    .Start(ctx =>
+    {
+        // Omitted
+    });
+```