@types/jest: Add inline snapshot matchers

[sebald]

Add the following matchers:

• toMatchInlineSnapshot
• toThrowErrorMatchingInlineSnapshot

Please fill in this template.

• Use a meaningful title for the pull request. Include the name of the package modified.
• Test the change in your own code. (Compile and run.)
• Add or edit tests to reflect the change. (Run with npm test.)
• Follow the advice from the readme.
• Avoid common mistakes.
• Run npm run lint package-name (or tsc if no tslint.json is present).

Select one of these and delete the others:

If adding a new definition:

• The package does not already provide its own types, or cannot have its .d.ts files generated via --declaration
• If this is for an NPM package, match the name. If not, do not conflict with the name of an NPM package.
• Create it with dts-gen --dt, not by basing it on an existing project.
• tslint.json should be present, and tsconfig.json should have noImplicitAny, noImplicitThis, strictNullChecks, and strictFunctionTypes set to true.

If changing an existing definition:

• Provide a URL to documentation or source code which provides context for the suggested changes: [RFC] Inline Snapshots jestjs/jest#6380
• Increase the version number in the header if appropriate.
• If you are making substantial changes, consider adding a tslint.json containing { "extends": "dtslint/dt.json" }.

If removing a declaration:

• If a package was never on DefinitelyTyped, you don't need to do anything. (If you wrote a package and provided types, you don't need to register it with us.)
• Delete the package's directory.
• Add it to notNeededPackages.json.

[sebald]

Hm, running tests from master -> they already fail ☹️

[typescript-bot]

@sebald Thank you for submitting this PR!

🔔 @NoHomey @jwbay @asvetliakov @alexjoverm @epicallan @ikatyang @wsmd @JamieMason @douglasduteil @ahnpnl @JoshuaKGoldberg @UselessPickles @r3nya @Hotell - please review this PR in the next few days. Be sure to explicitly select Approve or Request Changes in the GitHub UI so I know what's going on.

If no reviewer appears after a week, a DefinitelyTyped maintainer will review the PR instead.

[typescript-bot]

@sebald The Travis CI build failed! Please review the logs for more information.

Once you've pushed the fixes, the build will automatically re-run. Thanks!

[typescript-bot]

A definition owner has approved this PR ⭐️. A maintainer will merge this PR shortly. If it shouldn't be merged yet, please leave a comment saying so and we'll wait. Thank you for your contribution to DefinitelyTyped!