Windows: Add Qt6 and Editor install script

[Ghabry]

The buildscripts part to get the editor (soon) running again on Windows.

In short running build_editor.cmd and download_qt6.cmd gets everything setup.

The PR to the editor repo follows later. This needs a bit more work.

[Ghabry]

uhm have to shorten the triplet name a bit. I wonder since 2 days why CMake while buliding Kirigami reports "unknown error". Turns out I hit the 260 char path length limit 🤦 so have to tune everything to make it shorter. hmpf

Correction: Enabling Long path support also appears to work.

Run once as administrator in powershell

New-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Control\FileSystem" -Name "LongPathsEnabled" -Value 1 -PropertyType DWORD -Force

Have to document this.

[Ghabry]

Already documenting the workflow here to build the editor on Windows (PR for the Editor repo will come tomorrow):

Buildscripts:

1. Run build_editor.cmd
2. Run download_qt6.cmd
3. Run setup_env.cmd (if not already done due to Player development)

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Now in the Editor repository (inside a MSVC command prompt):

1. Run cmake --preset windows-x64-vs2022-liblcf-debug
2. Open the generated Visual Studio solution in build/win
3. Clicking Run will compile and execute the Editor

Note the difference with liblcf here: For the Player you need -DPLAYER_BUILD_LIBLCF=ON instead. I decided here to create another preset instead because we have far less target architectures here so the combinatorial explosion from all the presets is not as bad.

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For other editors (e.g. VS Code):

1. Configure the editor to use preset windows-x64-liblcf-debug
2. Run build/win/setup_env.cmd to configure the environment
3. Start coding

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For distribution:

1. Run cmake --build --preset windows-x64-vs2022-liblcf-debug --target install
2. You will find the binary and all dependencies in the "install" subdirectory