Support evaluation by extension

[timtucker-dte]

Data from mime-db also includes extensions -- would it make sense to have a second method that evaluates if a file is compressible based on its extension?

Looking for a common source of truth for decisions on whether or not to pre-compress files as part of our build process.

[dougwilson]

Sure, it can be added, but I think an issue with that is that typically an extension can refer to several different media types, some of which could differ in their compressibility. We'd need to provide some kind of mechanism to either resolve that case or maybe just always return undefined if a given extension refers to several different media types?