add ability to link to a particular mascot

[mansona]

I found myself wanting to link to the Empress mascot recently so I added the ability to link to a particular mascot using an ID.

Once this PR is merged you will be able to go to https://emberjs.com/mascots/#empress and it should scroll to the right part of the page and highlight the "target" mascot like this:

Let me know if you have any questions :)

Edit: here is a link with the preview app to allow you to test if it's working https://deploy-preview-805--ember-website.netlify.app/mascots/#empress