Add link to Real Python on editor

Fix typo

Fix sentence grammar

Thanks to John Thomas.

Remove whitespace to fix header rendering

Thanks to Jeremy (jmason)!

fix typo

Add details about some abbreviation and fixes

Fix errors reported by YAMLLint + use old Ubuntu

Trying older Ubuntu because of https://bugs.launchpad.net/ubuntu/+source/calibre/+bug/1884295

Use npx

https://github.com/honkit/honkit

Update about.md

Update translation_howto.md