Wider version range for click

[GabDug]

This MR simply extends the click dependency range, to include the 8.x series.
Click 8.x dropped support for Python 2 and 3.5, which are not supported by parglare.

There does not seem to be other breaking changes in click that impact the pglr command.

This is needed as more and more packages require click 8.x, and will provide a workaround for #26.

Code review checklist

• Pull request represents a single change (i.e. not fixing disparate/unrelated things in a single PR)
• Title summarizes what is changing
• Commit messages are meaningful (see this for details)
• Tests have been included and/or updated
• Docstrings have been included and/or updated, as appropriate
• Standalone docs have been updated accordingly
• Changelog(s) has/have been updated, as needed (see CHANGELOG.md, no need
  to update for typo fixes and such).

[igordejanovic]

LGTM. Thanks.