Auto-format displayed XAML for sample source code

# Problem

Source code for each sample is bundled into the final app output. This step is done manually, with one exception: UWP in release mode.

Under release mode, UWP already emits the XAML source files, but these files are slightly different than the original, with extra whitespace and an added `x:ConnectionId`.

The whitespace is especially problematic, as it breaks formatting and makes the XAML hard to read.

See this example: (click to expand)


# Solution
Rather than spending the time trying to custom emit these files to a different location, we can simply use a XAML formatter to fix the whitespace issue while unifying the formatting for all samples.