New mirrors

This MR serves to add new mirrors to the mirrorlist:

• https://crystal.kuchenmampfer.de/ --> Germany, offered by üüüüüüüüüü
• https://linuxgeeks.org/crystal/ --> US (Chicago), offered by SqnCdr
• https://crystal-repo.antiz.fr/ --> France (Strasbourg), offered by Antiz (me 😛)