Add diff-sequences package (#5407)

* Add diff-sequences package

* Update CHANGELOG.md

* Replace NOT_YET_USED with NOT_YET_SET

* Replace utility with command

* Tame prettier

* Add 4 tests

* Replace  with type cast to any

* Fix prettier errors

* Remove export from type declarations

* Correct aLength and bLength in README.md

Author: pedrottimark

CHANGELOG.md

@@ -2,6 +2,9 @@
 
 ### Features
 
+* `[diff-sequences]` New package compares items in two sequences to find a
+  **longest common subsequence**.
+  ([#5407](https://github.com/facebook/jest/pull/5407))
 * `[jest-config]` Allow lastComit and changedFilesWithAncestor via JSON config
   ([#5476](https://github.com/facebook/jest/pull/5476))
 * `[jest-util]` Add deletion to `process.env` as well

packages/diff-sequences/.npmignore

@@ -0,0 +1,3 @@
+**/__mocks__/**
+**/__tests__/**
+src