chore: prettier, markdownlint, cspell and fix many typos

[carlocorradini]

Related to PR #671

Keep in mind that this PR is purely focused to improving standards and maintainability.

What has been changed:

• Added prettier
• Added markdownlint
• Added cspell
• Added shellcheck
• Fix spelling typos
• Fix formatting (markdown and others)
• Moved CoC.md to root and renamed as CODE_OF_CONDUCT.md (standard and better for new contributors)

Scripts:

• npm run check
  Check for errors
• npm run fix
  Fix errors (if possible)

When the GitHub workflows are modified, npm run check has to be added