set PATH command is temporary

[ptr-dodge]

For windows install instruction, set PATH=%PATH%;"C:\tinygo\bin" will only set the path environment variable for that command prompt session. once you close the window it will be reset. Can we update this to make this change permanent by using setx /M path "%path%;C:\tinygo\bin"

[sago35]

It seems like a good idea to add the caveat, "setx ~~~~~~~ may be used if necessary."

[aykevl]

This sounds like a good idea.

@ptr-dodge if you want, you can make a PR to update the documentation here: https://github.com/tinygo-org/tinygo-site/blob/dev/content/getting-started/install/windows.md