[NonGNU ELPA] Package-Lint version 0.20

[ELPA update]

Version 0.20 of package Package-Lint has just been released in NonGNU ELPA.
You can now find it in M-x list-packages RET.

Package-Lint describes itself as:

  ===========================================
  A linting library for elisp package authors
  ===========================================

More at https://elpa.nongnu.org/nongnu/package-lint.html

## Summary:

  Provides a list of issues with the package metadata of a file,
  e.g. the package dependencies it requires.

  See function `package-lint-buffer'.

## Recent NEWS:

[Not available 🙁]