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