Update projects.yaml

[Aetherinox]

Add project mkdocs-link-embeds-plugin to CSS Styling subcategory.

What kind of change does this PR introduce?

• Add a project
• Update a project
• Remove a project
• Add or update a category
• Change configuration
• Documentation
• Other, please describe:

Description:

Add project mkdocs-link-embeds-plugin to HTML processing & CSS styling subcategory.

Plugin displays embedded links in a more stand-out fashion for a more direct presentation. Supports automatically fetching meta-data, ability to override values for custom listings.

Checklist:

• I have read the CONTRIBUTING guidelines.
• I have not modified the README.md file. Projects are only supposed to be added or updated within the projects.yaml file since the README.md file is automatically generated.

Notes:
I was unsure of either the CSS category, or [Links & references]. While my plugin does do auto generation of meta data, it's not a massive plugin that does major tasks like the ones listed in that category.

[pawamoy]

Thanks!

[Aetherinox]

You're very welcome, and thank you.