Docs: Add instructions for windows build from source

[dannyedel]

@projekter: I updated the installation/windows documentation with build-from-source instructions using your Dependency package.

Does this look okay to you?

Edit: Direct link to rendered source: https://github.com/dannyedel/dspdfviewer/blob/add-windows-build-from-source/installation/windows.md

[projekter]

Looks ok, although I doubt anyone would do themselves a favor compiling all this stuff ;).

[dannyedel]

We can always change the wording, I just wanted to save us (and especially you) some possible trouble. I'll merge it in.