Create a script for installing dependencies on Windows

We find a lot of times that the windows installation of gcc and go is non-trivial and can lead to messed up environments.

To automate this a script should be created that:
* installs Go (if it cannot be found)
* installs Gcc (if it cannot be found)
* Sets up appropriate environment variables

This needs to work for 32 and 64 bit systems.
It would also need to be decided which terminal to support - is this to work in PowerShell or should we use MSys2?
If the latter then a desktop shortcut may be needed to launch the "Fyne development" terminal...

Start by resolving the terminal choice raised in the issue: PowerShell or MSys2. Define how the installer detects Go and GCC, sets environment variables, and handles both 32-bit and 64-bit Windows systems. Done means a documented script installs missing dependencies and configures a usable Fyne development environment, including any required desktop shortcut.

Written by the indexing model from the issue text.