Update to version 3.000 of the fonts

[callegar]

Looks like upstream version 3.000 of the fonts has been released. Would it be possible to update to include those?

[MatthewVernon]

Version 4 was released in 2021 ( https://github.com/adobe-fonts/source-serif ), any chance of this package getting the update, please?

[tannenfreund87]

any chance of this package getting the update, please?

Version 4 changes the metrics, so to prevent documents from reflowing, the updated typeface should be in "sourceserif4"