Mirador/annotations plugins as submodules

• still need to rebuild the libs if modified
• replaced alpine (which can't build some npm deps because of musl) by debian

Closes #23 (closed)

added WF::2_doing label

requested review from @dbeniamine

added 8 commits

• 62d4a284...3468dfc8 - 7 commits from branch main
• a99912f0 - Mirador/annotations plugins as submodules

Compare with previous version

mentioned in commit 27bf3fa6

merged