#45 差分 API 作成

backend/Gemfile.lock

@@ -88,6 +88,7 @@ GEM
     connection_pool (2.5.3)
     crass (1.0.6)
     date (3.4.1)
+    diff-lcs (1.6.2)
     dotenv (3.1.8)
     drb (2.2.1)
     ed25519 (1.4.0)
@@ -412,6 +413,7 @@ PLATFORMS
 DEPENDENCIES
   bootsnap
   brakeman
+  diff-lcs
   gollum
   image_processing (~> 1.14)
   jwt