Add a `--version` flag, check version upon run and offer upgrade

[CallMeGreg]

1. Add a --version (or -v shorthand) flag to the root command to manually check the current version of the GH CLI extension.
2. When the gh language command is run, check the version of the extension. If there is a more recent release, offer to upgrade with gh extension upgrade CallMeGreg/gh-language as the first log statement before proceeding, as a warning.