feat(macros): remove mdn-data dependency

[argl]

Description

CSSInfo macro

This removes the dependency on mdn-data for the {{cssinfo}} macro. Data now comes solely from the contents of webref/css, except for translations of the values. The latter are now in a new translation file, living in content.

This is about the Formal defintion blocks on the CSS reference pages. These show up potentially on CSS properties and @-rule descriptors.

The legacy mdn-data-sourced localizations contained md/html/macro-enhanced content at times, linking to the data via enumerations. These enumerations along with any localizations, are not available in webref/css. After discussion with the content team it was deemed to be more important to reflect the specs from webref/css properly than any markup-regression we will see with this new approach.

The keys (inherited, animation type, …) are still translated as before, sourcing translations from content/files/jsondata/L10n-Template.json
Values are now translated from a new file in content/files/jsondata/L10n-CSSFormalDefinition.json. All translated languages are missing currently and can be filled in later. The current file includes the en-US values copied straight from the key.

CSS_ref macro

This macro used to be based on mdn-data, with numerous dead links in the resulting list. Since content has shifted away from the Wiki-style "link first, create the page second" mantra, we now base this macro on the actual content in the file system. This is in line with another macro {{APIListAlpha}} that simply walks the file system. This obviously removes the dependency on mdn-data

Motivation

Getting rid of mdn-data and go directly to the source.

Additional details

Related issues and pull requests

Fixes #369.