Update abia.md

Add description and molecular mechanism of AbiA #309 (closed)

added DefenseSystem label

requested review from @jcury

assigned to @ftesson

added 73 commits

• 807702ea...9fd810f9 - 71 commits from branch main
• 49565f7a - Merge branch 'main' into ftesson_abia
• 17d2d1df - merge main correct misspelling

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@jcury Problem with a modified file

closed