This is a workaround for microsoft/dtslint#281.

npm would end up deduping typescript@latest, since it encounters it first as a dependency of @definitelytyped/definitions‑parser and dts‑critic, then it would dedupe tslint, and lastly dtslint would get typescript@next:

node_modules/
	@definitelytyped/dtslint-runner/ 0.0.35
	@definitelytyped/definitions-parser/ 0.0.35
	dts-critic/ 3.2.3
	dtslint/ 3.6.6
		node_modules/
			typescript/ 4.0.0-dev
	tslint/ 5.14
	typescript/ 3.9.3

This results in microsoft/dtslint#281.

Adding typescript@next forces the node_modules structure to:

node_modules/
	@definitelytyped/dtslint-runner/ 0.0.35
	@definitelytyped/definitions-parser/ 0.0.35
		node_modules/
			typescript/ 3.9.3
	dts-critic/ 3.2.3
		node_modules/
			typescript/ 3.9.3
	dtslint/ 3.6.6
	tslint/ 5.14
	typescript/ 4.0.0-dev

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).

review?(@sandersn)