Use metadata values from the metadata block of the script

[FranklinYu]

Describe the change you'd like:

Name, Description (plain text), Homepage, and License fields are duplicated in the metadata block as @name, @description, @homepageURL, and @license. It would be lovely if we can optionally use the value in the metadata block.

Additional context:

N/A

[FranklinYu]

Implementation idea: we can either have an additional checkbox “inherit from code”, or we can tell users that empty value means inferring from Metadata block. The latter idea might not work well with the license field, though, as missing @license means all-rights-reserved.