Add CI for macOS and Windows documentation

Issue to track [PR 218](https://github.com/InsightSoftwareConsortium/ITKExamples/pull/218).

## Current behavior
CI successfully builds and publishes documentation for Ubuntu 18.04

## Desired behavior
CI successfully builds documentation for Windows, Ubuntu, and macOS platforms. Publishes documentation from Ubuntu 18.04 build only.

## Outstanding issues
Doxygen build fails:
> 2021-03-17T12:45:30.9574383Z [554/1581] cmd.exe /C "cd /D D:\a\ITKExamples\build && D:\a\_temp\-575274851\cmake-3.18.3-win64-x64\bin\cmake.exe -E echo "Finished obtaining Doxygen TAG""
2021-03-17T12:45:30.9575221Z Finished obtaining Doxygen TAG
2021-03-17T12:45:31.3548291Z [555/1581] Copying sources
2021-03-17T12:45:38.0276877Z [556/1581] Building CXX object src\CMakeFiles\ImageCompareCommand.dir\ImageCompareCommand.cxx.obj
2021-03-17T12:45:38.8736683Z [557/1581] Linking CXX executable bin\ImageCompareCommand.exe
2021-03-17T12:45:40.3933001Z [558/1581] Downloading and unpacking the Doxygen XML
2021-03-17T12:45:40.4024800Z FAILED: ITKDoxygenXML/index.xml
2021-03-17T12:45:40.4035015Z cmd.exe /C "cd /D D:\a\ITKExamples\build && D:\a\_temp\-575274851\cmake-3.18.3-win64-x64\bin\cmake.exe -DITKDoxygenXML_TEMP_DIR="D:/a/ITKExamples/build/ITKDoxygenXML-TEMP" -P D:/a/ITKExamples/ITKExamples/CMake/DownloadDoxygenXML.cmake && D:\a\_temp\-575274851\cmake-3.18.3-win64-x64\bin\cmake.exe -E chdir D:/a/ITKExamples/build/ITKDoxygenXML-TEMP D:/a/_temp/-575274851/cmake-3.18.3-win64-x64/bin/cmake.exe -E tar xjf D:/a/ITKExamples/build/ITKDoxygenXML-TEMP/itk-doxygen-xml.tar.bz2 && D:\a\_temp\-575274851\cmake-3.18.3-win64-x64\bin\cmake.exe -E rename D:/a/ITKExamples/build/ITKDoxygenXML-TEMP/xml D:/a/ITKExamples/build/ITKDoxygenXML && D:\a\_temp\-575274851\cmake-3.18.3-win64-x64\bin\cmake.exe -E remove_directory D:/a/ITKExamples/build/ITKDoxygenXML-TEMP"
2021-03-17T12:45:40.4044178Z -- [download 0% complete]
...
2021-03-17T12:45:40.5441963Z -- [download 100% complete]
2021-03-17T12:45:40.5507087Z Error renaming from "D:/a/ITKExamples/build/ITKDoxygenXML-TEMP/xml" to "D:/a/ITKExamples/build/ITKDoxygenXML": No error
2021-03-17T12:45:40.5509085Z [559/1581] Building CXX object src\Core\Common\CovariantVectorDotProduct\CMakeFiles\CovariantVectorDotProduct.dir\Code.cxx.obj

Review PR 218 and CMake/DownloadDoxygenXML.cmake first, then reproduce the reported Windows Doxygen XML failure in CI. Done means documentation builds on Windows, Ubuntu, and macOS, while publication remains limited to the Ubuntu 18.04 build.

索引モデルが issue の本文から書いたものです。