Following the docs doesn't give working results.

[crystalthoughts]

> npm i -D @custom-elements-manifest
> custom-elements-manifest analyze

custom-elements-manifest : The term 'custom-elements-manifest' is not recognized as the name of a cmdlet, function, script file, or operable program. Check the spelling 
of the name, or if a path was included, verify that the path is correct and try again.
At line:1 char:1
+ custom-elements-manifest analyze
+ ~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : ObjectNotFound: (custom-elements-manifest:String) [], CommandNotFoundException
    + FullyQualifiedErrorId : CommandNotFoundException

I get the above error.

I would prefix the last command with npx