release 2021-09-21 (new EPUB and PDF)

update ePub and PDF

- new LispWorks section
- re-written dates and times section (local-times library)
- updated database section, with updated Mito usage
- updated CI section with newer tools
- emacs: mentioned C-c C-j eval in repl
- iteration: about nconcing to return a flat list
- Added (clrhash) to data-structures.md
- more typo and grammar fixes, small additions

update ePub and PDF

from 1.1:

- more pattern matching, fixed guard example
- files: how to delete a directory
- web: explain more the error handling variables
- emacs-ide: fixed headings
- downloaded remaining images into assets/

update EPUB and PDF

update EPUB and PDF files