Required font files appear to be invalid

[davidmetzlaff]

I came across ggtech recently and it seemed like a great way to easily improve the design of my ggplots. However, there appear to be issues with the required font files which prevent them from being installed, at least on Windows 10.

1. When trying to install the fonts as described via extrafont, the installation fails due to error messages as described here
2. When trying to manually install the fonts into Windows, Windows argues that the file "is not a valid font file"
3. Online font file type converters are also unable to convert the file type of the font files claiming similar error messages as Windows
4. The Dropbox links are dead

Hope this helps!