GitHub Pages documentation support. (#5)

This PR contains the work done to:
* Update the `Library` article in the DocC documentation catalog in the project;
* Generate the DocC documentation of the library for GitHub Pages;
* Written the `README` file in the project.

Reviewed-on: #5
Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>
Co-committed-by: Javier Cicchelli <javier@rock-n-code.com>

docs/favicon.svg

@@ -0,0 +1,11 @@
+<!--
+  This source file is part of the Swift.org open source project
+
+  Copyright (c) 2021 Apple Inc. and the Swift project authors
+  Licensed under Apache License v2.0 with Runtime Library Exception
+
+  See https://swift.org/LICENSE.txt for license information
+  See https://swift.org/CONTRIBUTORS.txt for Swift project authors
+-->
+
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