Add other sorting options to the /contributing page

[hugodahl]

Currently, we can sort (or filter it seems like) the "Open Issues" portion of the /contributing page by the issue's label. It would be nice to have some age sorting options as well, such as "Oldest-Newest" and "Newest-Oldest" for various dates, such as the date it was opened, last active (comment/PR/other).

[hugodahl]

This could include (or perhaps a separate issue & pull request) displaying the time since any action was taken on the issue.