docs(jest-matcher-utils): README.md (#11942)

Author: mrienstra

packages/jest-matcher-utils/README.md

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+# jest-matcher-utils
+
+This package's exports are most notably used by `expect`'s [`this.utils`](https://jestjs.io/docs/expect#thisutils).
+
+## Installation
+
+To add this package as a dependency of a project, run either of the following commands:
+
+- `npm install jest-matcher-utils`
+- `yarn add jest-matcher-utils`
+
+## Exports ([src/index.ts](jest-matcher-utils/src/index.ts))
+
+### Functions
+
+`stringify` `highlightTrailingWhitespace` `printReceived` `printExpected` `printWithType` `ensureNoExpected` `ensureActualIsNumber` `ensureExpectedIsNumber` `ensureNumbers` `ensureExpectedIsNonNegativeInteger` `printDiffOrStringify` `diff` `pluralize` `getLabelPrinter` `matcherErrorMessage` `matcherHint`
+
+### Types
+
+`MatcherHintOptions` `DiffOptions`
+
+### Constants
+
+`EXPECTED_COLOR` `RECEIVED_COLOR` `INVERTED_COLOR` `BOLD_WEIGHT` `DIM_COLOR` `SUGGEST_TO_CONTAIN_EQUAL`