Add FreeFEM multiphysics finite element software from GitHub

This is a semi-regularly updated app used by Physicists. The main website is https://freefem.org/ and the actual software is hosted on GitHub.

There were 4 updates to this software in 2020, and the software install is consistent across versions (they use InnoSetup). In 2019 there were more updates (around 12 if I counted correctly) but, again, the installer has not changed.

Since it's hosted on GitHub they offer a json feed of the latest versions https://api.github.com/repos/FreeFem/FreeFem-sources/releases/latest

For what it's worth I use the following powershell for our evergreen process

$sourceAppInfo = Invoke-WebRequest -UseBasicParsing -Uri https://api.github.com/repos/FreeFem/FreeFem-sources/releases/latest  | ConvertFrom-Json


$sourceURI = $sourceAppInfo.assets | Where-Object name -Like "*-64.exe*" | Select-Object -ExpandProperty browser_download_url 


$exeVersion = $sourceAppInfo.tag_name

Thanks!