Badges for different kinds of content in product handbook

Why is this change being made?

It's hard to tell the difference between mandatory process and advice in the product handbook, so this adds a couple optional badges to make it more clear. This MR just updates one page as a first iteration, but this could be replicated out to other pages if agreed upon. You can see the badges on https://jyavorska-master-patch-60332.about.gitlab-review.app/handbook/product/index.html in a few places - I tried to choose non-controversial ones for an MVC.

Author Checklist

• Provided a concise title for the MR
• Added a description to this MR explaining the reasons for the proposed change, per say-why-not-just-what
• Assign this change to the correct DRI
  • If the DRI for the page/s being updated isn’t immediately clear, then assign it to your manager.
  • If your manager does not have merge rights, please ask someone to merge it AFTER it has been approved by your manager in #mr-buddies.
  • If the changes relate to any part of the project other than updates to content and/or data files please make sure to ping @gl-static-site-editor in a comment for a review and merge. For example changes to .gitlab-ci.yml, JavaScript/CSS/Ruby code or the layout files.

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