Add lesson or lesson section about css conventions

[bigacz]

Hello, I was thinking about adding some content in the curriculum about CSS conventions, most notably BEM.

What motivated me is that up to this point, CSS in my projects was a bit of a mess.
All of those non-standardized names and chains of descendant/child selectors discouraged me a lot.
Then, after using BEM in my newest project, styling things became a lot more enjoyable.

I came up with a few ways of including this content in the curriculum:

1. Creating a section in the Advanced Selectors lesson in the Intermediate HTML and CSS Course and adding a link to the BEM site in the assignment, and possibly their FAQ site

   Pros:

   • Could compare usage of descendant/child selectors vs. BEM.

   Cons:

   • This lesson is already a bit lenghty; adding another, not so tightly coupled concept might be overwhelming for the reader.

2. Adding a new lesson directly after the Advanced Selectors lesson.

   Pros:

   • Clearly separated from the previous lesson.

   Cons:

   • Might be a very short lesson.

3. Creating a new lesson in the Advanced HTML and CSS Course.

   Pros:

   • Could include content about separating CSS into multiple files as this content is after Webpack lessons.

   Cons:

   • Might feel a bit shoehorned; there isn't any relevant section in that course.

What do you think about this?