.pytool/Plugin: Add CI plugins

https://bugzilla.tianocore.org/show_bug.cgi?id=2315

Add .pytool directory to the edk2 repository with the
following plugins.  These plugins are in a top level
directory because that can be used with all packages
and platforms.

* CharEncodingCheck
* CompilerPlugin
* DependencyCheck
* DscCompleteCheck
* GuidCheck
* LibraryClassCheck
* SpellCheck

Cc: Sean Brogan <sean.brogan@microsoft.com>
Cc: Bret Barkelew <Bret.Barkelew@microsoft.com>
Cc: Liming Gao <liming.gao@intel.com>
Signed-off-by: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

.pytool/Plugin/CompilerPlugin/Compiler_plug_in.yaml

@@ -0,0 +1,11 @@
+## @file
+# CiBuildPlugin used to compile each package
+#
+# Copyright (c) Microsoft Corporation.
+# SPDX-License-Identifier: BSD-2-Clause-Patent
+##
+{
+  "scope": "cibuild",
+  "name": "Compiler Plugin",
+  "module": "CompilerPlugin"
+}