[TASK] rethink mdx file storage

[calvinhnzr]

sub slides should be rendered by selecting <h1>, <h2> tags or <SubSlide / > component

# current
./slides
    slide-000.mdx
    slide-010.mdx
    slide-020.mdx

# vision
./chapters
    ./one-1 # ./010-problem || ./chapter-010-problem || ./chapter-010
        slide-000.mdx # 000-detail.mdx ||  slide-000-detail.mdx || 000-slide-detail.mdx
        slide-010.mdx
        slide-010.mdx
    ./two-2
        slide-000.mdx
        slide-010.mdx
        slide-010.mdx

pros

• cleaner
• easier query
• less logic for axis flow

cons

• more work as an editor, creating files and folders

[calvinhnzr]