Windows build: Automate installing dependencies

Add a script buildtools/windows-deps-clickHere.bat that automates the process described on the "Compiling Inkscape on Windows" wiki page:

• Install MSYS, WiXv4 (via WinGet)
• Apply all MSYS upgrades, so that the script can also be used for updating
• Run msys2installdeps.sh
• Now also includes NSIS and 7-Zip

Tested: I can compile and start Inkscape on Win11. (Due to other issues with my VM, the graphics are corrupted, but that is not relevant for here.)

Draft text for a new section for the Wiki page:

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Automated installation

For the basic case (Inkscape 1.5-dev or newer with x64 architecture), you can use a one-click script file. In other cases, please follow the manual instructions further below.

• Get the buildtools folder from the Inkscape git repository. For example, download from the following link and unpack all files from ZIP. https://gitlab.com/inkscape/inkscape/-/archive/master/inkscape-master.zip?path=buildtools
• Double-click on windows-deps-clickHere.bat
• If you get a warning "Windows protected your PC. Microsoft Defender prevented an unrecognized app from starting.", click on "More information" and "Run anyway".
• Follow the instructions in the Terminal window. (Press Enter to confirm.)
• Confirm Administrator rights if Windows asks you to
• Wait a few hours until the script says Done. Then you can compile Inkscape as described later.

If something does not work, try to run the script again or follow the instructions for manual installation. Please also open an issue.