TypeScript detection filtering 'node_modules'.

Created by: holloway

See #5947 (closed).

verifyNoTypeScript checks whether there are any TypeScript files in the project during the build, and this PR refines that logic by adding a Globby negation filter so that any node_modules under ./src is excluded from this logic.

Considering that verifyNoTypeScript has only existed since CRA 2.1 it seems very unlikely that anyone would depend on checking in a node_modules for TypeScript support, so this is a safe change.

Steps to reproduce this bug and to show that this PR fixes it:

1. symlink ./src/anything to a directory outside the CRA project directory called anything.
2. npm init the anything with its own package.json that depends on big-integer. big-integer is distributed on NPM with TypeScript files which will be present at ./src/anything/node_modules/big-integer/BigInteger.d.ts.
3. Run yarn build and CRA ignores the TS and successfully builds.