Windows build instructions needs to be updated

[phob]

After installing VS Community 2017, QT 5.12 and looking all over the net for OpenSSL 1.1.1 for Windows because https://slproweb.com/products/Win32OpenSSL.html only provides OpenSSL 3.x

This gives me an error:
"C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Auxiliary\Build\vcvars32.bat" FOR /F "usebackq delims== tokens=2" %i IN (type stremio.pro ^| find "VERSION=4") DO set package_version=%i

FIND: Parameter format not correct
The process tried to write to a nonexistent pipe.
The process tried to write to a nonexistent pipe.
The syntax of the command is incorrect.

I can't continue in any way so the WINDOWS.md needs to be updated