Fix: pwsh scripts folder not there

[cjfullerton]

Host hpcflow, matflow folders not created so users making an install on a fresh system encountered an error.

[aplowman]

I tried running this in a Windows Sandbox (because it's always a "clean machine"), and found that I needed to:

• Add -UseBasicParsing to all of the Invoke-WebRequest commands, this is something to do with this command using some component of Internet Explorer
• Add -Force to the command New-Item -Path $profile -Type File which is used to create the profile file if it doesn't exist. In this case, this is necessary because one of the parent directories didn't exist.

I suggest we add these changes too. It is possible that someone might try to install on Windows Server for which these problems could feasibly exist.

[cjfullerton]

Have made the following changes:

• fixed typos
• Added -UseBasicParsing to Invoke-WebRequest calls
• Added -Force to New-Item calls (this should create parent directories where they don't exist).

@aplowman Feel free to test in Windows sandbox again when you have a moment.

[cjfullerton]

Merging as this version of the script runs on the integration test workflow.