Add comparison table design guidelines

[mmenestr]

We have no guidelines around what a comparison table should look like in PF. Need to add guidelines that cover the following things:

• Where the value vs parameter should be placed
• Whether to use vertical divider lines between items being compared
• Whether to use grey background color to distinguish parameter values / sticky column from rest of table, and if so, which shade

[mmenestr]

Doc: https://docs.google.com/document/d/1Z6LyyqYTxKxCtYwRVywttHjL7v15AFt7FyAXJB8zNK0/edit#heading=h.1iczefh0hkly