chore: migrate jest-diff to TypeScript

[SimenB]

Summary

Built diff:

diff --git c/packages/jest-diff/build/constants.js w/packages/jest-diff/build/constants.js
index 105f35736..2a0d2cd3e 100644
--- c/packages/jest-diff/build/constants.js
+++ w/packages/jest-diff/build/constants.js
@@ -16,8 +16,6 @@ function _interopRequireDefault(obj) {
  *
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
- *
- *
  */
 const NO_DIFF_MESSAGE = _chalk.default.dim(
   'Compared values have no visual difference.'
diff --git c/packages/jest-diff/build/diffStrings.js w/packages/jest-diff/build/diffStrings.js
index a5d12cadf..0dce819a0 100644
--- c/packages/jest-diff/build/diffStrings.js
+++ w/packages/jest-diff/build/diffStrings.js
@@ -9,7 +9,7 @@ var _chalk = _interopRequireDefault(require('chalk'));
 
 var _diffSequences = _interopRequireDefault(require('diff-sequences'));
 
-var _constants = require('./constants.js');
+var _constants = require('./constants');
 
 function _interopRequireDefault(obj) {
   return obj && obj.__esModule ? obj : {default: obj};
@@ -20,8 +20,6 @@ function _interopRequireDefault(obj) {
  *
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
- *
- *
  */
 const DIFF_CONTEXT_DEFAULT = 5;
 const fgPatchMark = _chalk.default.yellow;
diff --git c/packages/jest-diff/build/types.js w/packages/jest-diff/build/types.js
new file mode 100644
index 000000000..ad9a93a7c
--- /dev/null
+++ w/packages/jest-diff/build/types.js
@@ -0,0 +1 @@
+'use strict';

Test plan

Green CI

[SimenB]

easier than inspecting the arguments it takes

[codecov-io]

Codecov Report

Merging #7824 into master will decrease coverage by 0.58%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #7824      +/-   ##
==========================================
- Coverage   66.19%   65.61%   -0.59%     
==========================================
  Files         239      236       -3     
  Lines        9040     8861     -179     
  Branches        6        6              
==========================================
- Hits         5984     5814     -170     
+ Misses       3054     3045       -9     
  Partials        2        2

Impacted Files	Coverage Δ
packages/jest-circus/src/formatNodeAssertErrors.js	18.18% <ø> (ø)	⬆️
...ackages/jest-jasmine2/src/assertionErrorMessage.js	0% <ø> (ø)	⬆️

---

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[github-actions]

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