Update fs_giy_yig.md

Add description to FS_GIY_YIG system #314 (closed)

added DefenseSystem label

requested review from @jcury

assigned to @ftesson

added 36 commits

• faeaeb3b...99a0d69f - 34 commits from branch main
• ad25c571 - Merge branch 'main' into ftesson_giy_yig
• 7496308d - merge main correct misspelling

Compare with previous version

merged

mentioned in commit 53f4acc7