add viewport-fit to list of valid viewport directives

[Kilian]

This PR has three things:

• a fix for viewport-fit is flagged as invalid in viewport meta tag #110 that makes "viewport-fit" a valid option
• newly build dist packages with that change
• package-lock.json that's brought up to date with the current package.json

fixes #110

[Kilian]

Also included validation for the allowed values. I included the allowed values in the error message, which diverts from the other error messages but is more helpful.

[rviscomi]

Thanks for the PR!

Just one request, then could you also rerun the build script?

[rviscomi]

LGTM. Thanks again!