All CSSHelp methods need documentation

[ilenia-magoni]

From https://github.com/freeCodeCamp/curriculum-helpers/blob/main/lib/__tests__/css-helper.test.ts

I have resorted to consulting the test file to find out which methods to use, most of these don't have documentation:

• getStyle
• getStyleAny
• isPropertyUsed
• isDeclaredAfter
• getPropertyValue
• getCSSRules
• getRuleListsWithinMedia
• selectorsFromSelector

There are some docs in the curriculum-helpers repo, but all documentation should go in https://github.com/freeCodeCamp/contribute

[a2937]

The .getPropertyValue method is explained in the regular MDN Docs. Do I need to add some additional documentation about it on our pages?

[ilenia-magoni]

@a2937 I guess only mention that it is a native method that can be used on the output of getStyle