Support existing issues for `quick` command

What's Changed

• quick command can be used with just an issue number by @mattpolzin in #235
• Fix crash after marking PR ready by @mattpolzin in #247

harmony quick \#1234 is now short-hand for creating a branch locally for the given issue. This doesn't do much beyond git checkout -b feature/1234/whatever but it does allow you to accept-by-default a branch name built from the issue title. So if the issue title is "Fix a bug" then you can quickly and with few key-presses get a branch named bugfix/1234/fix-a-bug via harmony quick --bugfix \#1234.

Full Changelog: 6.2.0...6.3.0

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Install via npm with npm install --global @mattpolzin/harmony or by downloading the attached harmony-npm.tar.gz file, extracting, and then running npm install -g from the unzipped folder to install globally on your system. Use in a nix shell (assuming flakes are enabled) with nix shell github:mattpolzin/harmony. Install to your Nix profile with nix profile add github:mattpolzin/harmony.

You can build the source with Idris 2 v0.8.0 or the latest HEAD of the main Idris 2 branch.