feat: import upstream package (#25)

Author: github-actions[bot]

.github/UPSTREAM

@@ -1 +1 @@
-f80f3ff1d33581961cfa82f97175a12aa85b196a
+097b2179cd4eb86261dfd96c5841135408eb35ab

lcs/doc.go

@@ -139,7 +139,7 @@ computed labels. That is the worst case. Had the code noticed (x,y)=(u,v)=(3,3)
 from the edgegraph. The implementation looks for a number of special cases to try to avoid computing an extra forward path.
 
 If the two-sided algorithm has stop early (because D has become too large) it will have found a forward LCS and a
-backwards LCS. Ideally these go with disjoint prefixes and suffixes of A and B, but disjointness may fail and the two
+backwards LCS. Ideally these go with disjoint prefixes and suffixes of A and B, but disjointedness may fail and the two
 computed LCS may conflict. (An easy example is where A is a suffix of B, and shares a short prefix. The backwards LCS
 is all of A, and the forward LCS is a prefix of A.) The algorithm combines the two
 to form a best-effort LCS. In the worst case the forward partial LCS may have to