Improve Windows build documentation
Hi,
In light of the suggestions from @mashpoe in #774 (closed), this attempts to update the Windows build documentation in the following manner:
- Use MarkDown format, to make things more readable and browsable (and go back to UNIX line endings, for better consistency).
- Update info on the deps, in particular when building PangoFt2, where options need to be be passed into the Meson configuration line to enable things and ensuring the deps are correctly built in the process.
With blessings, thank you!