Add 'number' as type of arg accepted for its and invoke

[jennifer-shehane]

No description provided.

[bahmutov]

I have added an array example for cy.invoke and tested it in a fiddle

$ npm run dev -- --project ~/git/cypress-fiddle --config-file cypress-markdown.json

literally copy / paste documentation markdown

Running it

[bahmutov]

I do have to say the command log showing .1(4) looks funny. Maybe in case of a numerical index and a function we could show index and function's name