fix(docs): use recommended cjs import syntax for ts examples

[mleguen]

Fix typescript examples to use the right import syntax for a commonjs module such as yargs.

See explanation in typescript documentation here:

Both CommonJS and AMD generally have the concept of an exports object which contains all exports from a module.

[...]

When exporting a module using export =, TypeScript-specific import module = require("module") must be used to import the module.

[mleguen]

Closes #1511

[mleguen]

Closes #1455

[lf-]

@mleguen you have to put the "closes" in the initial PR message for GitHub to recognize it (you'll see an underline under "closes" when it's right)