Usage: vsce package|pack [options] [version]

Packages an extension

Options:
  -o, --out <path>                Output .vsix extension file to <path> location (defaults to <name>-<version>.vsix)
...
  --allow-missing-repository      Allow missing a repository URL in package.json
  --allow-unused-files-pattern    Allow include patterns for the files field in package.json that does not match any file
...

The following include patterns in the "files" property in package.json do not match any files packaged in the extension:
  - LICENSE
Remove any include pattern which is not needed.

=> Run vsce ls --tree to see all included files.
=> Use --allow-unused-files-patterns to skip this check