v4.0.0

• OpenPGP.js v5 (#78)
• POSIX-compliant inputs names (#109)
  • Rename gpg-private-key input gpg_private_key
  • Rename git-config-global input git_config_global
  • Rename git-user-signingkey input git_user_signingkey
  • Rename git-commit-gpgsign input git_commit_gpgsign
  • Rename git-tag-gpgsign input git_tag_gpgsign
  • Rename git-push-gpgsign input git_push_gpgsign
  • Rename git-committer-name input git_committer_name
  • Rename git-committer-email input git_committer_email
• Bump @actions/core from 1.4.0 to 1.5.0 (#106)