Prevent duplicate variable declaration error.

[ray-lee]

Description

This fixes a TypeScript compilation error that occurs because we now have both Mocha and Jest in the project. Both projects declare certain global variables with the same names, such as describe, it, and test, but different types. The fix configures TypeScript not to check every type definition file in node_modules/@types. Instead, it only checks the types that are imported by our source files. See https://www.typescriptlang.org/tsconfig#skipLibCheck.

Motivation and Context

Since we added Jest tests, the npm run build-docs script produces errors like:

node_modules/@types/mocha/index.d.ts:2733:13 - error TS2403: Subsequent variable declarations must have the same type.  Variable 'test' must be of type 'It', but here has type 'TestFunction'.

2733 declare var test: Mocha.TestFunction;
                 ~~~~

  node_modules/@types/jest/index.d.ts:43:13
    43 declare var test: jest.It;
                   ~~~~
    'test' was also declared here.

How Has This Been Tested?

The npm run build-docs should run without error. All other npm scripts should also contuinue to run without error.

Checklist:

• I have updated the documentation accordingly.
• All new and existing tests passed.

[tdilauro]

Tested. Looks good! 🥇