Content guidelines for component page type

[kurzn]

Next steps

• @sonnakim is working to apply the proposed guidelines for components to Tables by utilizing the outline from Modals
• @nkurz is working on completing the written component guidelines based on feedback from Modals and Tables

[sonnakim]

Here is the tables page rewrite: https://docs.google.com/document/d/1pHipfZ6uh4I2VUNMFeqF82tycJaWKaqyY5_MPYksc-M/edit#

I've sent this to @niqjohnson to get his feedback.