README links to BitSet/BitArray are 404's

[DivineDominion]

Just wanted to bring this up real quick: The current README.md lists BitSet and BitArray and links both to respective files in the Documentation/ folder -- but none of these exist. Couldn't see an obvious deletion from the commit messages; so is this WIP or did the files go missing, maybe?

[lorentey]

This is WIP -- we will either add these files as part of the 1.1.0 release preparation work, or we will simply link to DocC-generated documentation.

[DivineDominion]

Alright, feel free to close, then!