Check download availability

I would like to suggest a feature that when opening the installation modal, hydra checks the links of the fonts (Seeds, gofile, pixeldrain and etc.) to avoid problems with downloads that don't start and especially to show only the functional links for fonts with multiple links.

Ex: If you have 2 links, 1 from gofile and another from pixeldrain but the gofile is invalid, only show pixeldrain.

(If you don't have something else to consider, I'd be happy to make a Pr for this feature)