Migrate content from wiki

doc/crashpad.doxy.h

-// Copyright 2014 The Crashpad Authors. All rights reserved.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-#error This file is not intended to be #included.
-
-//! \namespace crashpad
-//! \brief The main namespace.
-
-//! \namespace crashpad::internal
-//! \brief The internal namespace, not for public use.
-
-//! \namespace crashpad::test
-//! \brief The testing namespace, for use in test code only.